Proprietary software is

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consist ...

that is deemed within the

free and open-source software Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...

to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a

legal monopoly A legal monopoly, statutory monopoly, or ''de jure'' monopoly is a monopoly that is protected by law from competition. A statutory monopoly may take the form of a government monopoly where the state owns the particular means of production or govern ...

afforded by modern

copyright A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, educatio ...

and

intellectual property law Intellectual property (IP) is a category of property that includes intangible creations of the human intellect. There are many types of intellectual property, and some countries recognize more than others. The best-known types are patents, cop ...

to exclude the recipient from freely sharing the software or modifying it, and—in some cases, as is the case with some patent-encumbered and

EULA An end-user license agreement or EULA () is a legal contract between a software supplier and a customer or end-user, generally made available to the customer via a retailer acting as an intermediary. A EULA specifies in detail the rights and res ...

-bound software—from making use of the software on their own, thereby restricting his or her freedoms. It is often contrasted with

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized so ...

free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, n ...

. For this reason, it is also known as non-free software or closed-source software.

Types

Origin

Until the late 1960s computers—large and expensive

mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...

s, machines in specially air-conditioned computer rooms—were usually

lease A lease is a contractual arrangement calling for the user (referred to as the ''lessee'') to pay the owner (referred to as the ''lessor'') for the use of an asset. Property, buildings and vehicles are common assets that are leased. Industrial ...

d to customers rather than

sold Sold may refer to: * ''Sold'' (Boy George album), 1987 * ''Sold'' (Died Pretty album), 1996 * ''Sold'' (TV series), a British comedy drama television series * ''Sold'' (McCormick novel), a 2006 novel by Patricia McCormick and Illustrated by Br ...

. Service and all software available were usually supplied by manufacturers without separate charge until 1969. Computer vendors usually provided the source code for installed software to customers. Customers who developed software often made it available to others without charge. Closed source means computer programs whose source code is not published except to licensees. It is available to be edited only by the organization that developed it and those licensed to use the software. In 1969, IBM, which had

antitrust Competition law is the field of law that promotes or seeks to maintain market competition by regulating anti-competitive conduct by companies. Competition law is implemented through public and private enforcement. It is also known as antitrust ...

lawsuits pending against it, led an industry change by starting to charge separately for mainframe software and services, by unbundling hardware and software.

Bill Gates William Henry Gates III (born October 28, 1955) is an American business magnate and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions ...

' " Open Letter to Hobbyists" in 1976 decried computer hobbyists' rampant

copyright infringement Copyright infringement (at times referred to as piracy) is the use of works protected by copyright without permission for a usage where such permission is required, thereby infringing certain exclusive rights granted to the copyright holder, ...

of software, particularly Microsoft's Altair BASIC interpreter, and asserted that their unauthorized use hindered his ability to produce quality software. But the legal status of

software copyright Software copyright is the application of copyright in law to machine-readable software. While many of the legal principles and policy debates concerning software copyright have close parallels in other domains of copyright law, there are a number ...

, especially for

object code In computing, object code or object module is the product of a compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ...

, was not clear until the 1983 appeals court ruling in Apple Computer, Inc. v. Franklin Computer Corp. According to

Brewster Kahle Brewster Lurton Kahle ( ; born October 21, 1960)Alexa Internet profile
, via juggle.com. accessed Novemb ...

the legal characteristic of software changed also due to the U.S.

Copyright Act of 1976 The Copyright Act of 1976 is a United States copyright law and remains the primary basis of copyright law in the United States, as amended by several later enacted copyright provisions. The Act spells out the basic rights of copyright holders, cod ...

.Robert X
Cringely's interview with Brewster Kahle
46th minute Starting in February 1983 IBM adopted an " object-code-only" model for a growing list of their software and stopped shipping much of the source code, even to licensees. In 1983, binary software became copyrightable in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

as well by the Apple vs. Franklin law decision, before which only source code was copyrightable. Additionally, the growing availability of millions of computers based on the same microprocessor architecture created for the first time an unfragmented and big enough market for binary distributed software.

Legal basis

Most of the software is covered by

which, along with

contract law A contract is a legally enforceable agreement between two or more parties that creates, defines, and governs mutual rights and obligations between them. A contract typically involves the transfer of goods, services, money, or a promise to t ...

patents A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...

, and

trade secret Trade secrets are a type of intellectual property that includes formulas, practices, processes, designs, instruments, patterns, or compilations of information that have inherent economic value because they are not generally known or readily ...

s, provides legal basis for its owner to establish exclusive rights. A software vendor delineates the specific terms of use in an

end-user license agreement An end-user license agreement or EULA () is a legal contract between a software supplier and a customer or end-user, generally made available to the customer via a retailer acting as an intermediary. A EULA specifies in detail the rights and rest ...

(EULA). The user may agree to this contract in writing, interactively on screen ( clickwrap), or by opening the box containing the software ( shrink wrap licensing). License agreements are usually not negotiable.

Software patent A software patent is a patent on a piece of software, such as a computer program, libraries, user interface, or algorithm. Background A patent is a set of exclusionary rights granted by a state to a patent holder for a limited period of time ...

s grant exclusive rights to algorithms, software features, or other patentable subject matter, with coverage varying by jurisdiction. Vendors sometimes grant patent rights to the user in the license agreement. The

source code In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the ...

for a piece of propietary software is routinely handled as a

. Software can be made available with fewer restrictions on licensing or source-code access; software that satisfies certain conditions of freedom and openness is known as " free" or "

Limitations

Since license agreements do not override applicable

copyright law A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, educatio ...

, provisions in conflict with applicable law are not enforceable. Some software is specifically licensed and not sold, in order to avoid limitations of copyright such as the first-sale doctrine.

Exclusive rights

The owner of proprietary software exercises certain

exclusive right In Anglo-Saxon law, an exclusive right, or exclusivity, is a de facto, non-tangible prerogative existing in law (that is, the power or, in a wider sense, right) to perform an action or acquire a benefit and to permit or deny others the right t ...

s over the software. The owner can restrict the use, inspection of source code, modification of source code, and redistribution.

Use of the software

Vendors typically limit the number of computers on which software can be used, and prohibit the user from installing the software on extra computers. Restricted use is sometimes enforced through a technical measure, such as product activation, a

product key A product key, also known as a software key, serial key or activation key, is a specific software-based key for a computer program. It certifies that the copy of the program is original. Product keys consist of a series of numbers and/or letters ...

or serial number, a hardware key, or

copy protection Copy protection, also known as content protection, copy prevention and copy restriction, describes measures to enforce copyright by preventing the reproduction of software, films, music, and other media. Copy protection is most commonly found o ...

. Vendors may also distribute versions that remove particular features, or versions which allow only certain fields of endeavor, such as non-commercial, educational, or non-profit use. Use restrictions vary by license: *

Windows Vista Starter Windows Vista—a major release of the Microsoft Windows operating system—was available in six different product editions: Starter, Home Basic, Home Premium, Business, Enterprise, and Ultimate. On September 5, 2006, Microsoft announced the USD p ...

is restricted to running a maximum of three concurrent applications. * The retail edition of Microsoft Office Home and Student 2007 is limited to non-commercial use on up to three devices in one household. *

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was release to manufacturing, released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Wind ...

can be installed on one computer, and limits the number of network file sharing connections to 10. The Home Edition disables features present in Windows XP Professional. * Traditionally,

Adobe Adobe ( ; ) is a building material made from earth and organic materials. is Spanish for '' mudbrick''. In some English-speaking regions of Spanish heritage, such as the Southwestern United States, the term is used to refer to any kind of ...

licenses are limited to one user, but allow the user to install a second copy on a home computer or laptop. This is no longer true with the switching to Creative Cloud. * iWork '09, Apple's productivity suite, is available in a five-user family pack, for use on up to five computers in a household.

Inspection and modification of source code

Vendors typically distribute proprietary software in

compiled In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs tha ...

form, usually the

machine language In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a ver ...

understood by the computer's

central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...

. They typically retain the

, or human-readable version of the software, often written in a higher level programming language. This scheme is often referred to as closed source. While most proprietary software is distributed without the source code, some vendors distribute the source code or otherwise make it available to customers. For example, users who have purchased a license for the Internet forum software vBulletin can modify the source for their own site but cannot redistribute it. This is true for many web applications, which must be in source code form when being run by a web server. The source code is covered by a

non-disclosure agreement A non-disclosure agreement (NDA) is a legal contract or part of a contract between at least two parties that outlines confidential material, knowledge, or information that the parties wish to share with one another for certain purposes, but wis ...

or a license that allows, for example, study and modification, but not redistribution. The text-based email client

Pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family (biology), family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanic ...

and certain implementations of

Secure Shell The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Its most notable applications are remote login and command-line execution. SSH applications are based ...

are distributed with proprietary licenses that make the source code available.Some licenses for proprietary software allow distributing changes to the source code, but only to others licensed for the product, and some of those modifications are eventually picked up by the vendor. Some governments fear that proprietary software may include defects or malicious features which would compromise sensitive information. In 2003 Microsoft established a Government Security Program (GSP) to allow governments to view source code and Microsoft security documentation, of which the Chinese government was an early participant. The program is part of Microsoft's broader Shared Source Initiative which provides source code access for some products. The Reference Source License (Ms-RSL) and Limited Public License (Ms-LPL) are proprietary software licenses where the source code is made available. Governments have also been accused of adding such malware to software themselves. According to documents released by

Edward Snowden Edward Joseph Snowden (born June 21, 1983) is an American and naturalized Russian former computer intelligence consultant who leaked highly classified information from the National Security Agency (NSA) in 2013, when he was an employee and su ...

, the

NSA The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence (DNI). The NSA is responsible for global monitoring, collec ...

has used covert partnerships with software companies to make commercial encryption software exploitable to eavesdropping, or to insert backdoors. Software vendors sometimes use obfuscated code to impede users who would reverse engineer the software. This is particularly common with certain

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

s. For example, the

bytecode Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (norma ...

for programs written in

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...

can be easily decompiled to somewhat usable code, and the source code for programs written in

scripting language A scripting language or script language is a programming language that is used to manipulate, customize, and automate the facilities of an existing system. Scripting languages are usually interpreted at runtime rather than compiled. A scripting ...

s such as PHP or

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

is available at run time.

Redistribution

Proprietary software vendors can prohibit the users from sharing the software with others. Another unique license is required for another party to use the software. In the case of proprietary software with source code available, the vendor may also prohibit customers from distributing their modifications to the source code.

Shareware Shareware is a type of proprietary software that is initially shared by the owner for trial use at little or no cost. Often the software has limited functionality or incomplete documentation until the user sends payment to the software developer ...

is closed-source software whose owner encourages redistribution at no cost, but which the user sometimes must pay to use after a trial period. The fee usually allows use by a single user or computer. In some cases, software features are restricted during or after the trial period, a practice sometimes called crippleware.

Interoperability with software and hardware

Proprietary file formats and protocols

Proprietary software often stores some of its data in file formats that are incompatible with other software, and may also communicate using protocols which are incompatible. Such formats and protocols may be restricted as

s or subject to

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...

Proprietary APIs

A proprietary

application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

(API) is a

software library In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and sub ...

interface "specific to one device or, more likely to a number of devices within a particular manufacturer's product range." The motivation for using a proprietary API can be

vendor lock-in In economics, vendor lock-in, also known as proprietary lock-in or customer lock-in, makes a customer dependent on a vendor for products, unable to use another vendor without substantial switching costs. The use of open standards and alternat ...

or because standard APIs do not support the device's functionality. The

European Commission The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body ...

, in its March 24, 2004, decision on Microsoft's business practices, quotes, in paragraph 463, Microsoft general manager for C++ development Aaron Contorer as stating in a February 21, 1997, internal Microsoft memo drafted for

: :The

Windows API The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces (APIs) available in the Microsoft Windows operating systems. The name Windows API collectively refers to several different platform implementations th ...

is so broad, so deep, and so functional that most ISVs would be crazy not to use it. And it is so deeply embedded in the source code of many Windows apps that there is a huge switching cost to using a different operating system instead. Early versions of the iPhone SDK were covered by a

. The agreement forbade independent developers from discussing the content of the interfaces. Apple discontinued the NDA in October 2008.

Vendor lock-in

Any dependency on the future versions and upgrades for a proprietary software package can create ''vendor lock-in'', entrenching a monopoly position.

Software limited to certain hardware configurations

Proprietary software may also have licensing terms that limit the usage of that software to a specific set of hardware.

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...

has such a licensing model for

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...

, an operating system which is limited to Apple hardware, both by licensing and various design decisions. This licensing model has been affirmed by the

United States Court of Appeals for the Ninth Circuit The United States Court of Appeals for the Ninth Circuit (in case citations, 9th Cir.) is the U.S. federal court of appeals that has appellate jurisdiction over the U.S. district courts in the following federal judicial districts: * District ...

Abandonment by proprietors

Proprietary software which is no longer marketed, supported or sold by its owner is called abandonware, the digital form of orphaned works. If the proprietor of a software package should cease to exist, or decide to cease or limit production or support for a proprietary software package, recipients and users of the package may have no recourse if problems are found with the software. Proprietors can fail to improve and support software because of business problems. Support for older or existing versions of a software package may be ended to force users to upgrade and pay for newer versions( planned obsolescence). Sometimes another vendor or a software's community themselves can provide support for the software, or the users can migrate to either competing systems with longer support life cycles or to FOSS-based systems. Some proprietary software is released by their owner at end-of-life as open-source or

source available Source-available software is software released through a source code distribution model that includes arrangements where the source can be viewed, and in some cases modified, but without necessarily meeting the criteria to be called open-sour ...

software, often to prevent the software from becoming unsupported and unavailable abandonware.

3D Realms 3D Realms Entertainment ApS is a video game publisher based in Aalborg, Denmark. Scott Miller (entrepreneur), Scott Miller founded the company in his parents' home in Garland, Texas, in 1987 as Apogee Software Productions to release his game ' ...

and id Software are famous for the practice of releasing closed source software into the

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized so ...

. Some of those kinds are free-of-charge downloads (

freeware Freeware is software, most often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines ''freeware'' unambiguously; every publisher defines its own rules for the ...

), some are still commercially sold (e.g.

Arx Fatalis ''Arx Fatalis'' is an action role-playing video game developed by Arkane Studios and released for Microsoft Windows in 2002 and Xbox in 2003. The game is played from a first-person perspective and is set on a world whose sun has failed, forcing t ...

). More examples of formerly closed-source software in the

List of commercial software with available source code This is a list of proprietary source-available software, which has available source code, but is not classified as free software or open-source software. In some cases, this type of software is originally sold and released without the source code, ...

and

List of commercial video games with available source code This is a list of commercial video games with available source code. The source code of these commercially developed and distributed video games is available to the public or the games' communities. In several of the cases listed here, the g ...

Pricing and economics

Proprietary software is not synonymous with

commercial software Commercial software, or seldom payware, is a computer software that is produced for sale or that serves commercial purposes. Commercial software can be proprietary software or free and open-source software. Background and challenge While sof ...

, although the two terms are sometimes used synonymously in articles about free software. Proprietary software can be distributed at no cost or for a fee, and

can be distributed at no cost or for a fee. The difference is that whether proprietary software can be distributed, and what the fee would be, is at the proprietor's discretion. With free software, anyone who has a copy can decide whether, and how much, to charge for a copy or related services. Proprietary software that comes for no cost is called

. Proponents of commercial proprietary software argue that requiring users to pay for software as a product increases funding or time available for the

research and development Research and development (R&D or R+D), known in Europe as research and technological development (RTD), is the set of innovative activities undertaken by corporations or governments in developing new services or products, and improving existi ...

of software. For example,

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washi ...

says that per-copy fees maximize the profitability of software development. Proprietary software generally creates greater commercial activity over free software, especially in regard to market revenues. Proprietary software is often sold with a license that gives the end user right to use the software.

Examples

Examples of proprietary software include

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...

Adobe Flash Player Adobe Flash Player (known in Internet Explorer, Firefox, and Google Chrome as Shockwave Flash) is computer software for viewing multimedia contents, executing rich Internet applications, and streaming audio and video content created on ...

, PS3 OS,

Orbis OS The PlayStation 4 system software is the updatable firmware and operating system of the PlayStation 4. The operating system is Orbis OS, based on FreeBSD 9. Technology System The native operating system of the PlayStation 4 is Orbis OS, which ...

iTunes iTunes () is a software program that acts as a media player, media library, mobile device management utility, and the client app for the iTunes Store. Developed by Apple Inc., it is used to purchase, play, download, and organize digital mu ...

Adobe Photoshop Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Windows and macOS. It was originally created in 1988 by Thomas and John Knoll. Since then, the software has become the industry standard not only in rast ...

Google Earth Google Earth is a computer program that renders a 3D computer graphics, 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposition, superimposing satellite images, aerial photography, and geog ...

(formerly Mac OS X and OS X),

Skype Skype () is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls. It also has instant messaging, file transfer, debi ...

WinRAR WinRAR is a trialware file archiver utility for Windows, developed by Eugene Roshal of win.rar GmbH. It can create and view archives in RAR or ZIP file formats, and unpack numerous archive file formats. To enable the user to test the integrit ...

, Oracle's version of

, Huawei's

HarmonyOS HarmonyOS (HMOS) () is a distributed operating system developed by Huawei to collaborate and interconnect with multiple smart devices on the Internet of Things (IoT) ecosystem. In its current multi-kernel design, the operating system select ...

and some versions of

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, ...

. Software distributions considered as proprietary may in fact incorporate a "mixed source" model including both free and non-free software in the same distribution. Most if not all so-called proprietary

UNIX Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, ...

distributions are mixed source software, bundling open-source components like

BIND BIND () is a suite of software for interacting with the Domain Name System (DNS). Its most prominent component, named (pronounced ''name-dee'': , short for ''name daemon''), performs both of the main DNS server roles, acting as an authoritative ...

Sendmail Sendmail is a general purpose internetwork email routing facility that supports many kinds of mail-transfer and delivery methods, including the Simple Mail Transfer Protocol (SMTP) used for email transport over the Internet. A descendant of the ...

X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...

DHCP The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a cli ...

, and others along with a purely proprietary kernel and system utilities. Some free software packages are also simultaneously available under proprietary terms. Examples include

MySQL MySQL () is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A relational database ...

and ssh. The original copyright holders for a work of free software, even copyleft free software, can use dual-licensing to allow themselves or others to redistribute proprietary versions. Non-copyleft free software (i.e. software distributed under a permissive free software license or released to the public domain) allows anyone to make proprietary redistributions. Free software that depends on proprietary software is considered "trapped" by the Free Software Foundation. This includes software written only for Microsoft Windows, or software that could only run on

, before it became free software.

References

External links

* {{DEFAULTSORT:Proprietary Software Software licenses