On Dec 3, 2007 12:59 PM, drew Roberts zotz@100jamz.com wrote:

OK, CC BY is not copyleft at all.

CC BY-SA as it stands now is a weak copyleft (as we are speaking of weak here)

This is, however, a disputed point: CC-By-SA even includes examples of new works which would be required to be cc-by-sa licensed, such as the movie which results from adding images or video to a covered sound recording.

From by-sa-2.5: "'Derivative Work' means a work based upon the Work

or upon the Work and other pre-existing works, (...) or any other form in which the Work may be recast, transformed, or adapted, except that a work that constitutes a Collective Work will not be considered a Derivative Work for the purpose of this License. For the avoidance of doubt, where the Work is a musical composition or sound recording, the synchronization of the Work in timed-relation with a moving image ("synching") will be considered a Derivative Work for the purpose of this License."

When Creative Commons adopted the position that cc-by-sa covered images do not enjoy the same protection as sound in situations where it is synchronized with sound or text it was shocking and upsetting to a number of people.

So while it's the whole weak/strong copyleft issue needs to be fleshed out, I don't think it's fair to just state that cc-by-sa is currently a weak copyleft, even if that is the intention of the licenses' stewards with respect to visual works.