Hey, something I can answer! Well, from what I understand, these model packs can be used in DBP and FPSC. So, FPSC is NOT manditory, as long as you buy it, it works with all TGC programs...I believe. Correct me if I'm wrong. Though, I am not sure if you can use, or if they are even compatible, with C++ etc. Anything you buy from TGC can be sold in a game. So, if I buy MP6 and throw it in my game, I can sell the game. I hope that answers your question.
"When all of hell breaks loose, I will be laughing at the people believing a god will save them."