Share Alike

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SA, aka Share Alike.

The Share Alike aspect requires 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. 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. This is in contrast to the Attribution-only license from CC where a derivative could be released under full copyright restrictions (All Rights Reserved).

As changes have been made to the Creative Commons licenses over the years there have been 4 versions of the BY-SA and BY-NC-SA licenses (1.0, 2.0, 2.5, and 3.0) Creative Commons has taken steps to ensure that works licensed under one particular version of the Creative Commons Attribution ShareAlike license can be incorporated with a work from a later version. Specifically, any work that is licensed with a BY-SA or BY-NC-SA version 2.0 or higher can be used with any later version of the license. For specifics see the chart below.

  A Derivative can use the corresponding license version:
If the original work
1.0 2.0 2.5 3.0
BY-SA version 1.0        
BY-NC-SA version 1.0        
BY-SA version 2.0        
BY-NC-SA version 2.0        
BY-SA version 2.5        
BY-NC-SA version 2.5        
BY-SA version 3.0        
BY-NC-SA version 3.0        

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.

The following was contributed by anonymous trolls in 2004. It is rather amazing that it was not ported into this wiki from its predecessor rather than continuing to be enhanced. An exact definition of this concept is one of the foundations of CC itself.

The Share Alike option of the Creative Commons public license is a specific interpretation of the general share-alike ideal which is also found in copyleft (i.e. Free Software).

share with (some) others

The SA license is similar to a consortium license or other peer group contracts.

The CC concept of Share Alike means strictly and only "share with (some) others on the same terms they have shared with you". It does not require that this sharing be with "everyone" as in "copyleft". Though that is an option (the CC-by-sa for instance) in the CC parametric license regime it is not a universal: the CC-by-nc-sa for instance does not share with commercial parties. In this sense it is like a sort of nonprofit consortium license.

shareware, science, documentation

Its general concept of sharing might include for instance a:

not all Common Content is SA

Share Alike is orthogonal to Common Content as the latter includes both SA and non-SA terms on that content.

open content, free software are SA

The generic idea of share-alike is probably the base concept of open content, Free Software, which apply additional requirements that SA alone doesn't:

  • open content requires more careful specific attribution
  • Free Software requires sharing with literally everyone

Accordingly it is possible to bring both of these ultimately into the parametric license regime both as SA licenses.

open source is not SA

Open source requires sharing with literally everyone but does not require them to share back with you - they can make their own proprietary extensions and enhancements and can withhold them. Accordingly open source is simply not SA but is more like the CC-by - though open source does not in many cases guarantee credit or any means of creator validation. It is a simple gift to everyone that can be used against its creator, or against its creator's values.