As i know you can Sell your models or your models in a game you don`t have to give any credits or anything to program , as long as YOU MADE THEM in that program , they`r yours to sell or do whatever you like with them. ONLY things that are prohibet are : DECOMPILING OF THE PROGRAM OR DISSASEMBLING OR ANYHOW GETTING THE SOURCE CODE , and if you have any premade models in program ( i mean models that you just like drag into the workfield , that are finished ) they are most likely owned by company of the program and there for learning purpoises , so you cannot sell them in game or anyhow , but anything you made you should have no troubles with selling or anything.