April's dead on. After 4 years of paying attention to such stuff, I can't think of any single poser place that is selling anything where that use is considered acceptable under the terms of the EULA's in force. Furthermore, even if the mesh is converted, it is still being redistributed, which violates every EULA in force at present as well (the converted mesh, be it in obj, c4d, purple haze, or whatever -- even x format -- is still derivative, and the same method that is used to convert it can be used to return it to the format delivered, in, making it extractable under the current terms of law for the EULA's at present). Pretty much, unless written authorization exists specifically form individual merchants pertaining specifically to that mesh/texture/other item, they are violating the terms of the agreement under which they use it.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)