According to previous posts from the folks at Zygote, (I don't have any links to the threads) meshes are copyrighted to the creator. Anything made using even one vertex of the original model still falls under the copyright of the original creator. Your renders are yours, provided you follow the requirements specified by the readme files accompanying any third party downloads (props, textures, etc...) you use. I don't know if Zygote has said anything about Cr2s or morphs, but I would suspect that they would fall under the copyright of the original creator, as well, including combinations of meshes/characters from the same source.