Just to clear things up: 1) Making a render that features someone's mesh does not infringe the copyright of the maker of the mesh. Redistributing the mesh does. 2) Placing a restriction as to what sort of picture a prop can be used in has no legal force whatsoever. 3) If you flout the restriction, the mesh maker has no comeback against you at all, BUT he/she will be majorly pissed off and probably stop contributing to free stuff in future. Your call.