Mason, have you done around a 20% change to these models? If so, then you could claim them as your own, and I don't think anyone would complain too hard, if at all. Plus you have to consider that the person that posted them over there in the first place may have done the same thing- Changed a bit here and there. Therefore, in addition to his changes and your changes, it's that much changes from the original. Just be sure to place in the readme the little history in how the models came into existance on your DL page.