Which Creative Commons ShareAlike license versions are compatible with each other?
Version 1.0 of the CC licenses containing the ShareAlike provision are not compatible with later versions of the ShareAlike licenses. If you wish to make an adaptation of a work licensed under BY-SA 1.0, for example, then the resulting adaptation must also be licensed under BY-SA 1.0. All of the ShareAlike licenses starting from version 2.0 are compatible with future versions of the ShareAlike licenses. If you want to make an adaptation using a photograph that is licensed under a BY-SA 2.0 license, you can apply BY-SA 3.0 to the adaptation. The licenses are not backward compatible, however. You cannot create an adaptation of a work licensed under BY-SA 3.0 and license the derivative under BY-SA 2.0. Access the license versions page to compare the versions of the licenses on this point and others.
