On 2/23/07, Stephen Bain stephen.bain@gmail.com wrote:
Or give them the extremely quick summary: the viral nature of copyleft licences (the "share-alike" provisions) prevents commercial exploitation while allowing commercial innovation.
That is, unfortunately, not quite true. For images in particular, CC-BY-SA provides no meaningful protection from commercial exploitation. An article using a CC-BY-SA picture is _not_ considered a derivative; only any direct modifications to the picture trigger the share-alike clause.
We are currently discussing alternatives on the cc-licenses list that would trigger share-alike on strongly semantically linked combinations as well -- but the current license does not do that.
Strangely enough, the existing CC-BY-SA license _does_ consider the combination of music and a film a derivative work that would require the whole film to be copyleft -- but not the embedding of images into an article.