Share-alike

The Creative Commons icon for Share-Alike, a variant of the copyleft symbol

Share-Alike is a descriptive term used in the Creative Commons project for copyright licenses which include certain copyleft provisions. The Share-Alike license comes in two varieties, CC-BY-SA and CC-BY-NC-SA.

Share-alike license types

As all Creative Commons licenses, share-alike licenses require attribution. Share-alike means that all derivatives of a work to be licensed under the same (or a compatible) license as the original. Thus, if a person were to use parts of a BY-SA movie to create a new short film, that new short film would also need to be licensed as BY-SA. 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 Share-Alike license is similar to the GNU Project's General Public License (GPL) and Free Documentation License (GFDL).

There are two varieties of Share-Alike licenses. The first, CC-BY-SA, allows commercial use. The second, CC-BY-NC-SA, which requires non-commercial use, only is Share-Alike but is not free content (and not copyleft, according to some critics).

CC-BY-SA and Free Culture Works

Creative Commons Attribution-ShareAlike licenses are based on the principles of the Free Software movement. As applied to content, these principles require a license to grant the following essential freedoms to ALL users of licensed works:

• the freedom to use the work and enjoy the benefits of using it
• the freedom to study the work and to apply knowledge acquired from it
• the freedom to make and redistribute copies, in whole or in part, of the information or expression
• the freedom to make changes and improvements, and to distribute derivative works

These 4 freedoms are taken directly from the Definition of Free Culture Works

By contrast, there are also many permissive free software licences which do not require share-alike terms to be applied, thus permitting users to make modifications and improvements and apply a modified and more restrictive license.

History of ShareAlike Versions

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 - Released December, 2002[1]
  • Attribution-NonCommerical-ShareAlike Version 1.0 Generic[2]

• Attribution-ShareAlike Version 2.0 Generic - Released May, 2004[3]
  • Attribution-NonCommerical-ShareAlike Version 2.0 Generic[4]

• Attribution-ShareAlike Version 2.5 Generic - Released June, 2005[5]
  • Attribution-NonCommerical-ShareAlike Version 2.5 Generic[6]

• Attribution-ShareAlike Version 3.0 Unported - Released March, 2007[7]
  • Attribution-NonCommerical-ShareAlike Version 3.0 Unported[8]

  The 3.0 licenses added a compatibility clause. Creative Commons may declare a license compatible with ShareAlike, allowing it to be used instead of the exact same license for derivatives.

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. This decision was hailed by many as a win for Free Culture as well as visionary leadership.

See also

• Copyleft
• Wikipedia's cc-by-sa license

External links

• Creative Commons licenses explained
• Wikipedia:Text of Creative Commons Attribution-ShareAlike 3.0 Unported License
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