HOME

TheInfoList



OR:

A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and redistribute that software. These actions are usually prohibited by
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 ...
law, but the rights-holder (usually the author) of a piece of software can remove these restrictions by accompanying the software with a
software license A software license is a legal instrument (usually by way of contract law, with or without printed material) governing the use or redistribution of software. Under United States copyright law, all software is copyright protected, in both sourc ...
which grants the recipient these rights. Software using such a license is free software (or
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 ...
) as conferred by the copyright holder. Free-software licenses are applied to
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 ...
in
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 ...
and also binary object-code form, as the copyright law recognizes both forms.


Comparison

Free-software licenses provide risk mitigation against different legal threats or behaviors that are seen as potentially harmful by developers:


History


Pre-1980s

In the early times of software, sharing of software and source code was common in certain communities, for instance academic institutions. Before the US Commission on New Technological Uses of Copyrighted Works (CONTU) decided in 1974 that "computer programs, to the extent that they embody an author's original creation, are proper subject matter of copyright",Lemley, Menell, Merges and Samuelson. ''Software and Internet Law'', p. 34. software was not considered copyrightable. Therefore, software had no licenses attached and was shared as
public-domain software Public-domain software is software that has been placed in the public domain, in other words, software for which there is absolutely no ownership such as copyright, trademark, or patent. Software in the public domain can be modified, distributed, ...
. The CONTU decision plus court decisions such as '' Apple v. Franklin'' in 1983 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 ...
, clarified that the Copyright Act gave computer programs the copyright status of literary works and started the licensing of software. Free-software licenses before the late 1980s were generally informal notices written by the developers themselves. These early licenses were of the " permissive" kind.


1980s

In the mid-1980s, the
GNU project The GNU Project () is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and computing devices by collabor ...
produced
copyleft Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
free-software licenses for each of its software packages. An early such license (the "GNU Emacs Copying Permission Notice") was used for
GNU Emacs GNU Emacs is a free software text editor. It was created by GNU Project founder Richard Stallman, based on the Emacs editor developed for Unix operating systems. GNU Emacs has been a central component of the GNU project and a flagship project ...
in 1985, which was revised into the "GNU Emacs General Public License" in late 1985, and clarified in March 1987 and February 1988. Likewise, the similar GCC General Public License was applied to the
GNU Compiler Collection The GNU Compiler Collection (GCC) is an optimizing compiler produced by the GNU Project supporting various programming languages, hardware architectures and operating systems. The Free Software Foundation (FSF) distributes GCC as free softwar ...
, which was initially published in 1987. The original BSD license is also one of the first free-software licenses, dating to 1988. In 1989, version1 of the
GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general ...
(GPL) was published. Version2 of the GPL, released in 1991, went on to become the most widely used free-software license.


1990s to 2000s

Starting in the mid-1990s and until the mid-2000s, 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 ...
movement pushed and focused the free-software idea forward in the wider public and business perception. In the
Dot-com bubble The dot-com bubble (dot-com boom, tech bubble, or the Internet bubble) was a stock market bubble in the late 1990s, a period of massive growth in the use and adoption of the Internet. Between 1995 and its peak in March 2000, the Nasdaq Comp ...
time, Netscape Communications' step to release its webbrowser under a FOSS license in 1998, inspired many other companies to adapt to the FOSS ecosystem. In this trend companies and new projects (
Mozilla Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, spreads and supports Mozilla products, thereby promoting exclusively free software and open standards, ...
,
Apache foundation The Apache Software Foundation (ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open source software projects. The ASF was formed from a group of developers of the Ap ...
, and Sun, see also this list) wrote their own FOSS licenses, or adapted existing licenses. This
License proliferation License proliferation is the phenomenon of an abundance of already existing and the continued creation of new software licenses for software and software packages in the FOSS ecosystem. License proliferation affects the whole FOSS ecosystem ...
was later recognized as problem for the
Free and open-source 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 ...
ecosystem due to the increased complexity of
license compatibility License compatibility is a legal framework that allows for pieces of software with different software licenses to be distributed together. The need for such a framework arises because the different licenses can contain contradictory requiremen ...
considerations. While the creation of new licenses slowed down later, license proliferation and its impact are considered an ongoing serious challenge for the free and open-source ecosystem. From the free-software licenses, the GNU GPL version2 has been tested in to court, first in Germany in 2004 and later in the USA. In the German case the judge did not explicitly discuss the validity of the GPL's clauses but accepted that the GPL had to be adhered to: "If the GPL were not agreed upon by the parties, defendant would notwithstanding lack the necessary rights to copy, distribute, and make the software 'netfilter/iptables' publicly available." Because the defendant did not comply with the GPL, it had to cease use of the software. The US case (
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 ...
vs Progress) was settled before a verdict was arrived at, but at an initial hearing, Judge Saris "saw no reason" that the GPL would not be enforceable. Around 2004 lawyer Lawrence Rosen argued in the essay ''Why the public domain isn't a license'' software could not truly be waived into public domain and can't be interpreted as very permissive FOSS license, a position which faced opposition by Daniel J. Bernstein and others. In 2012 the dispute was finally resolved when Rosen accepted the CC0 as
open source license An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. This allows end users and commercial comp ...
, while admitting that contrary to his previous claims copyright can be waived away, backed by
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 ...
decisions. In 2007, after years of draft discussion, the GPLv3 as major update of the GPLv2 was released. The release was controversial due to the significant extended scope of the license, which made it incompatible with the GPLv2. Several major FOSS projects (
Linux kernel The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU ...
,
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 ...
,
BusyBox BusyBox is a software suite that provides several Unix utilities in a single executable file. It runs in a variety of POSIX environments such as Linux, Android, and FreeBSD, although many of the tools it provides are designed to work with inte ...
, Blender, VLC media player) decided against adopting the GPLv3. On the other hand, in 2009, two years after the release of the GPLv3,
Google Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
open-source programs office manager Chris DiBona reported that the number of open-source projects licensed software that had moved to GPLv3 from GPLv2 was 50%, counting the projects hosted at
Google Code Google Developers (previously Google Code) , application programming interfaces (APIs), and technical resources. The site contains documentation on using Google developer tools and APIs—including discussion groups and blogs for developers usin ...
.


2010s

In 2011, four years after the release of the GPLv3, 6.5% of all open-source licensed projects were GPLv3 while 42.5% were still GPLv2 according to Black Duck Software data. Following in 2011 ''451 Group'' analyst Matthew Aslett argued in a blog post that copyleft licenses went into decline and permissive licenses increased, based on statistics from Black Duck Software. In 2015 according to Black Duck Software and
GitHub GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, cont ...
statistics, the permissive
MIT license The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts only very limited restriction on reuse and has, therefore, high license comp ...
dethroned the GPLv2 as most popular free-software license to the second place while the permissive Apache license follows already at third place. In June 2016 an analysis of
Fedora Project The Fedora Project is an independent project to co-ordinate the development of Fedora Linux, a Linux-based operating system, operating with the vision of "''a world where everyone benefits from free and open source software built by inclusive, w ...
's packages revealed as most used licenses the GPL, MIT, BSD, and the
LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
.


Definitions


OSI-approved open-source licenses

The group
Open Source Initiative The Open Source Initiative (OSI) is the steward of the Open Source Definition, the set of rules that define open source software. It is a California public-benefit nonprofit corporation, with 501(c)(3) tax-exempt status. The organization wa ...
(OSI) defines and maintains a list of approved
open-source license An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. This allows end users and commercial com ...
s. OSI agrees with FSF on all widely used free-software licenses, but differ from FSF's list, as it approves against the Open Source Definition rather than the
Free Software Definition The Free Software Definition written by Richard Stallman and published by the Free Software Foundation (FSF), defines free software as being software that ensures that the end users have freedom in using, studying, sharing and modifying that so ...
. It considers Free Software Permissive license group to be a reference implementation of a Free Software license. Thus its requirements for approving licenses are different.


FSF-approved free-software licenses

The
Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed under copyleft ( ...
, the group that maintains the
Free Software Definition The Free Software Definition written by Richard Stallman and published by the Free Software Foundation (FSF), defines free software as being software that ensures that the end users have freedom in using, studying, sharing and modifying that so ...
, maintains a non-exhaustive list of free-software licences. The Free Software Foundation prefers
copyleft Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
(
share-alike Share-alike (đź„Ž) is a copyright licensing term, originally used by the Creative Commons project, to describe works or licenses that require copies or adaptations of the work to be released under the same or similar license as the original. Cop ...
) free-software licensing rather than permissive free-software licensing for most purposes. Its list distinguishes between free-software licenses that are compatible or incompatible with the FSF's copyleft
GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general ...
.


Conditions in free-software licenses

There exists an ongoing debate within the
free-software community The free software movement is a social movement with the goal of obtaining and guaranteeing certain freedoms for software users, namely the freedoms to run the software, to study the software, to modify the software, and to share copies of the s ...
regarding the fine line between what restrictions can be applied and still be called "free". Only "
public-domain software Public-domain software is software that has been placed in the public domain, in other words, software for which there is absolutely no ownership such as copyright, trademark, or patent. Software in the public domain can be modified, distributed, ...
" and software under a public-domain-like license is restriction-free. Examples of public-domain-like licenses are, for instance, the WTFPL and the CC0 license.
Permissive license A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, ...
s might carry small obligations like attribution of the author but allow practically all code use cases. Certain licenses, namely the
copyleft license Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose, ...
s, include intentionally stronger restrictions (especially on the distribution/distributor) in order to force derived projects to guarantee specific rights which can't be taken away.


Copyleft

The free-software share-alike licenses written by
Richard Stallman Richard Matthew Stallman (; born March 16, 1953), also known by his initials, rms, is an American free software movement activist and programmer. He campaigns for software to be distributed in such a manner that its users have the freedom to ...
in the mid-1980s pioneered a concept known as "copyleft". Ensuing copyleft provisions stated that when modified versions of free software are distributed, they must be distributed under the same terms as the original software. Hence they are referred to as "share and share alike" or "''quid pro quo''". This results in the new software being open source as well. Since copyleft ensures that later generations of the software grant the freedom to modify the code, this is "free software". Non-copyleft licenses do not ensure that later generations of the software will remain free. Developers who use GPL code in their product must make 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 ...
available to anyone when they share or sell the
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 ...
. In this case, the source code must also contain any changes the developers may have made. If GPL code is used but not shared or sold, the code is not required to be made available and any changes may remain private. This permits developers and organizations to use and modify GPL code for private purposes (that is, when the code or the project is not sold or otherwise shared) without being required to make their changes available to the public. Supporters of GPL claim that by mandating that derivative works remain under the GPL, it fosters the growth of free software and requires equal participation by all users. Opponents of GPL claim that "no license can guarantee future software availability" and that the disadvantages of GPL outweigh its advantages. Some also argue that restricting distribution makes the license less free. Whereas proponents would argue that not preserving freedom during distribution would make it less free. For example, a non-copyleft license does not grant the author the freedom to see modified versions of his or her work if it gets publicly published, whereas a copyleft license does grant that freedom.


Patent retaliation

During the 1990s, free-software licenses began including clauses, such as
patent retaliation Opposition to software patents is widespread in the free software community. In response, various mechanisms have been tried to defuse the perceived problem. Positions from the community Community leaders such as Richard Stallman, Alan Cox, ...
, in order to protect against
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 ...
litigation cases – a problem which had not previously existed. This new threat was one of the reasons for writing version3 of the GNU GPL in 2006. In recent years, a term coined
tivoization Tivoization is the practice of designing hardware that incorporates software under the terms of a copyleft software license like the GNU General Public License (GNU GPL), but uses hardware restrictions or digital rights management (DRM) to preve ...
describes a process where hardware restrictions are used to prevent users from running modified versions of the software on that hardware, in which the TiVo device is an example. It is viewed by the FSF as a way to turn free software to effectively non-free, and is why they have chosen to prohibit it in
GPLv3 The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general u ...
. Most newly written free-software licenses since the late 1990s include some form of patent retaliation clauses. These measures stipulate that one's rights under the license (such as to redistribution), may be terminated if one attempts to enforce patents relating to the licensed software, under certain circumstances. As an example, the
Apple Public Source License The Apple Public Source License (APSL) is the open-source and free software license under which Apple's Darwin operating system was released in 2000. A free and open-source software license was voluntarily adopted to further involve the communi ...
may terminate a user's rights if said user embarks on litigation proceedings against them due to patent litigation. Patent retaliation emerged in response to proliferation and abuse of
software patents 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, u ...
.


Hardware restrictions

Version3 of the GNU GPL includes specific language prohibiting additional restrictions being enforced by
hardware restrictions A hardware restriction (sometimes called hardware DRM) is low-level protection enforced by electronic components. The hardware restriction scheme may protect against physical or malware attacks or complement a digital rights management system imp ...
and digital rights management (DRM), a practice FSF calls
tivoization Tivoization is the practice of designing hardware that incorporates software under the terms of a copyleft software license like the GNU General Public License (GNU GPL), but uses hardware restrictions or digital rights management (DRM) to preve ...
after Tivo used GPL’d software on devices that disallowed user modification of that software.


Attribution, disclaimers and notices

The majority of free-software licenses require that modified software not claim to be unmodified. Some licenses also require that copyright holders be credited. One such example is version2 of the GNU GPL, which requires that interactive programs that print warranty or license information, may not have these notices removed from modified versions intended for distribution.


Practical problems with licenses


License compatibility

Licenses of software packages containing contradictory requirements render it impossible to combine source code from such packages in order to create new software packages. License compatibility between a
copyleft license Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose, ...
and another license is often only a one-way compatibility. This "one-way compatibility" characteristic is, for instanced, criticized by the
Apache Foundation The Apache Software Foundation (ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open source software projects. The ASF was formed from a group of developers of the Ap ...
, who provides the more permissive Apache license which doesn't have this characteristic. Non-copyleft licenses, such as the FOSS
permissive licenses A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, ...
, have a less complicated license interaction and normally exhibit better license compatibility. For example, if one license says "modified versions must mention the developers in any advertising materials", and another license says "modified versions cannot contain additional attribution requirements", then, if someone combined a software package which uses one license with a software package which uses the other, it would be impossible to distribute the combination because these contradictory requirements cannot be fulfilled simultaneously. Thus, these two packages would be license-incompatible. When it comes to
copyleft Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
software licenses, they are not inherently compatible with other copyleft licenses, even the GPLv2 is, by itself, not compatible with the GPLv3.


Purpose of use

Restrictions on use of a software ("use restrictions") are generally unacceptable according to the FSF, OSI,
Debian Debian (), also known as Debian GNU/Linux, is a Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of De ...
, or the BSD-based distributions. Examples include prohibiting that the software be used for non-private applications, for military purposes, for comparison or benchmarking, for good use, for ethically questionable means, or in commercial organizations. While some restrictions on user freedom, e.g. concerning nuclear war, seem to enjoy moral support among most free software developers, it is generally believed that such agendas should not be served through software licenses; among other things because of practical aspects such as resulting legal uncertainties and problems with enforceability of vague, broad and/or subjective criteria or because tool makers are generally not held responsible for other people’s use of their tools. Nevertheless some projects include legally non-binding pleas to the user, prominently
SQLite SQLite (, ) is a database engine written in the C programming language. It is not a standalone app; rather, it is a library that software developers embed in their apps. As such, it belongs to the family of embedded databases. It is the mo ...
. Among the repeated attempts by developers to regulate user behavior through the license that sparked wider debate are
Douglas Crockford Douglas Crockford is an American computer programmer who is involved in the development of the JavaScript language. He specified the data format JSON (JavaScript Object Notation), and has developed various JavaScript related tools such as the st ...
’s (joking) “no evil” clause, which affected the release process of the Debian distribution in 2012 and got the JSMin-PHP project expelled from
Google Code Google Developers (previously Google Code) , application programming interfaces (APIs), and technical resources. The site contains documentation on using Google developer tools and APIs—including discussion groups and blogs for developers usin ...
, the addition of a pacifist condition based on Asimov’s First Law of Robotics to the GPL for the distributed computing software ''GPU'' in 2005, as well as several software projects trying to exclude use by big cloud providers.


Definition conflicts

As there are several defining organizations and groups who publish definitions and guidelines about FOSS licenses, notably the FSF, the OSI, the Debian project, and the BSDs, there are sometimes conflicting opinions and interpretations.


Permissive versus copyleft opinions

Many users and developers of BSD-based operating systems have a different position on licensing. The main difference is the belief that the
copyleft Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
licenses, particularly the
GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general ...
(GPL), are undesirably complicated and/or restrictive. The GPL requires any derivative work to also be released according to the GPL while the
BSD license BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...
does not. Essentially, the BSD license's only requirement is to acknowledge the original authors, and poses no restrictions on how 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 ...
may be used. As a result, BSD code can be used in
proprietary software Proprietary software is software that is deemed within the free and open-source software to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a legal monopoly afforded by modern copyright and i ...
that only acknowledges the authors. For instance, Microsoft Windows NT 3.1 and
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 ...
have proprietary
IP stack The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the sui ...
s which are derived from BSD-licensed software. In extreme cases, the sub- or re-licensing possibilities with BSD or other permissive licenses might prevent further use in the open-source ecosystem. For instance,
MathWorks MathWorks is an American privately held corporation that specializes in mathematical computing software. Its major products include MATLAB and Simulink, which support data analysis and simulation. History The company's key product, MATLAB, wa ...
' FileExchange repository offers the BSD license for user contributions but prevents with additional terms of use any usage beside their own
proprietary {{Short pages monitor