 CC BY-SA

This one strikes the right balance between restriction and permissions. NC and ND are simply too restrictive.

TODO where does the SA boundary end? E.g.:

Does source code need to be redistributed: opensource.stackexchange.com/questions/1849/does-the-cc-by-sa-license-require-that-source-code-of-derivative-works-be-shared

Case law list on the CC wiki: wiki.creativecommons.org/wiki/Category:Case_Law