Share-alike (🄎) 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.

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 are free content or

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, no ...

licenses with a share-alike condition. Two currently-supported Creative Commons licenses have the ShareAlike condition: Creative Commons Attribution-ShareAlike (a

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 content license) and Creative Commons Attribution-NonCommercial-ShareAlike (a proprietary license). The term has also been used outside copyright law to refer to a similar plan for

patent licensing A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...

Copyleft

Copyleft or libre share-alike licenses are the largest subcategory of share-alike licenses. They include both free content licenses like Creative Commons Attribution-ShareAlike and

licenses like 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 ...

. These licenses have been described pejoratively as viral licenses, because the inclusion of copyleft material in a larger work typically requires the entire work to be made copyleft. The term reciprocal license has also been used to describe copyleft, but has also been used for non-libre licenses (see, for example, the

Microsoft Limited Reciprocal License The Shared Source Initiative (SSI) is a Source-available software, source-available Software license, software licensing scheme launched by Microsoft in May 2001. The program includes a spectrum of technologies and licenses, and most of its source ...

). Free content and software licenses without the share-alike requirement are described as permissive licenses.

Creative Commons

As with all six licenses in the current Creative Commons suite, CC Attribution-ShareAlike and CC Attribution-NonCommercial-ShareAlike require attribution. According to Creative Commons, the advantage of this license is that future users are not able to add new restrictions to a derivative of your work; their derivatives must be licensed the same way. The 3.0 and 4.0 version of the ShareAlike licenses include a compatibility clause, allowing Creative Commons to declare other licenses as compatible and therefore derivatives may use these instead of the license of the original work.

Version history

Over the years, Creative Commons has issued 5 versions of the BY-SA and BY-NC-SA licenses (1.0, 2.0, 2.5, 3.0 and 4.0). *Attribution-ShareAlike Version 1.0 Generic and Attribution-NonCommercial-ShareAlike Version 1.0 Generic – Released December, 2002 *Attribution-ShareAlike Version 2.0 Generic and Attribution-NonCommercial-ShareAlike Version 2.0 Generic – Released May, 2004 *Attribution-ShareAlike Version 2.5 Generic and Attribution-NonCommercial-ShareAlike Version 2.5 Generic – Released June, 2005 *Attribution-ShareAlike Version 3.0 Unported and Attribution-NonCommercial-ShareAlike Version 3.0 Unported – Released March, 2007 *Attribution-ShareAlike Version 4.0 International and Attribution-NonCommercial-ShareAlike Version 4.0 International – Released November, 2013

Adoption

In June 2009 the

Wikipedia community The Wikipedia community, collectively known colloquially as Wikipedians, is an informal community that volunteers to create and maintain Wikipedia, an online encyclopedia. Since August 2012, the word "Wikipedian" has been an '' Oxford Diction ...

and

Wikimedia Foundation The Wikimedia Foundation, Inc., or Wikimedia for short and abbreviated as WMF, is an American 501(c)(3) nonprofit organization headquartered in San Francisco, California and registered as a charitable foundation under local laws. Best know ...

board approved the adoption of the Creative Commons Attribution-ShareAlike (CC BY-SA) license as the main content license for Wikipedia and other Wikimedia sites. Creative Commons hailed this decision as a victory for

free culture The free-culture movement is a social movement that promotes the freedom to distribute and modify the creative works of others in the form of free content or Free content, open content without compensation to, or the consent of, the work's origin ...

as well as visionary leadership.

References

{{intellectual property activism Public copyright licenses Copyleft Free software Creative Commons vi:Giấy phép Creative Commons#Chia sẻ tương tự

Copyleft

Creative Commons

Version history

Adoption

See also

References