I think Creative Commons is and was a great effort, but I think they made one critical mistake, the non-commerical clause. I can understand that at first glance that making it possible to limit ‘commercial use’ seems like a good idea, at least in order to get people onto the idea of copyleft style licensing, but in practicality it kills the basic purpose of the license, to allow people to freely copy.
Christian Schaller – Where Creative Commons botched
Creative Commons are the biggest promoter of NonCommercial licenses, and it’s hard to promote pure copyleft against that. :-/