A few days ago i joined #[url=mailto:[email protected]][email protected][/url] to ask about it, and this is what a guy told me:
Considering the GPL models an input for building an output (renderings) this output may be GPL too. That is, free to use, BUT when models/input are GPL that's a different story. Of course there is no problem by using the CCA models (just attribution required).

So your reasoning seems to be the correct one. If i don't want to make GPL my renderings i should use just CCA models. Otherwise i have to publish them under GPL.

Regards