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 was:||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.