This sounds like on of those tangles that would need an expensive court case to settle. I expect that there is a body of precendent to define phrases such as "substantially similar", but how much could be applied to 3D models? It's certainly an ask-a-lawyer question, and that's not in my budget. How many content creators could pay the fee from their Poser revenue? How many will just, as you intend, play safe? I hope you've misunderstood, but can I afford to take the chance?