How about this: Play nice? 1) Respect the creator's wishes. 2) If you're not sure, e-mail the creator and ask. Personally, I think that the creator owns the model while you own the final image. If you make money off of the model with the rendering, you might want to consider repaying that creator in some way (if feasible.) Not because you are obliged to, but because you ought to. HandSpanStudios nailed it on the head.