Share-alike
Share-alike is a copyright licensing term, originally used by the Creative Commons project, to describe works or licences that require copies or adaptations of the work to be released under the same or similar licence as the original.[1] Copyleft licences are free content or free software licences with a share-alike condition.
Two currently-supported Creative Commons licences have the ShareAlike condition: Creative Commons Attribution-ShareAlike (a copyleft, free content licence) and Creative Commons Attribution-NonCommercial-ShareAlike (a proprietary licence).
The term has also been used outside of copyright law to refer to a similar plan for patent licensing.[2]
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[edit] Copyleft
Copyleft or reciprocal licences are the largest subcategory of share-alike licences. They include both free content licences like Creative Commons Attribution-ShareAlike and free software licences like the GNU General Public License. These licences have been described pejoratively as viral licences, because the inclusion of copyleft material in a larger work typically requires the entire work to be made copyleft.
Free content and software licences without the requirement of reciprocity are described as permissive licences or copyfree.
[edit] Creative Commons
As with all six licences 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.[3]
Although CC Attribution-ShareAlike qualifies as copyleft because it is free content, CC Attribution-NonCommercial-ShareAlike is non-free and therefore not copyleft.[4]
The 3.0 version of the ShareAlike licenses had an added a compatibility clause, allowing Creative Commons to declare a license compatible with one of their ShareAlike licences, allowing it to be used instead of the exact same license for derivatives.
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Over the years, Creative Commons has issued 4 versions of the BY-SA and BY-NC-SA licenses (1.0, 2.0, 2.5, and 3.0).
- Attribution-ShareAlike Version 1.0 Generic[1] and Attribution-NonCommerical-ShareAlike Version 1.0 Generic[2] - Released December, 2002
- Attribution-ShareAlike Version 2.0 Generic[3] and Attribution-NonCommerical-ShareAlike Version 2.0 Generic[4] - Released May, 2004
- Attribution-ShareAlike Version 2.5 Generic[5] and Attribution-NonCommerical-ShareAlike Version 2.5 Generic[6] - Released June, 2005
- Attribution-ShareAlike Version 3.0 Unported[7] and Attribution-NonCommerical-ShareAlike Version 3.0 Unported[8] - Released March, 2007
[edit] Adoption
In June, 2009 the Wikipedia community and Wikimedia Foundation 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.[5] Creative Commons hailed this decision was hailed as a victory for free culture as well as visionary leadership.[6]
[edit] References
- ^ "Glossary". http://opendatahandbook.org/en/glossary.html#term-share-alike-license. Retrieved 2012-03-05.
- ^ "Share-Alike Patents". http://blog.iandavis.com/2011/08/08/share-alike-patents/. Retrieved 2012-03-05.
- ^ "Share Alike". http://wiki.creativecommons.org/Share_Alike. Retrieved 2010-12-17.
- ^ "NonCommercial Sharealike is not Copyleft". http://robmyers.org/weblog/2008/02/noncommercial-sharealike-is-not-copyleft.html.
- ^ http://en.wikipedia.org/wiki/Wikipedia:Text_of_Creative_Commons_Attribution-ShareAlike_3.0_Unported_License
- ^ "Wikipedia + CC BY-SA = Free Culture Win!". http://creativecommons.org/weblog/entry/15411.
