I disagree, A good example is poser meshes. If you make morphs the morphs themselves are yours but as the original mesh is used to create the morph, you cannot even give the morph away to someone that doesn't own the original mesh without violating copyright unless you get permission. Textures - if you put a different texture on a mesh you can give away thar texture but still not the mesh. If you were to paint a mushstashe on a rendering of the Mona Lisa and filter it so it looked blue you would still be technically in voilation although You're probably safe from the wrath of da Vinci. Again; it's a good idea get permission.