Quote: they are copyrighted characters, but if you are doing a fan based free game, i dont see a problem as long as you dont try to claim the rights to the characters
They are copyrighted characters hence you cannot use them without the copyright holders permission. The law is very clear on this: Fan Games of copyrighted material ARE illegal no matter what your commercial intent.
The only way these models can be used legally is if you are using them as an educational project or you keep them private in your own home... any public or commercial aspiration to use them and you are doing so "at your own risk".
Just be careful with copyright and follow the general rule: if you don't own it, don't use it. I don't mean to be a buzz kill, but the whole legality of Fan Games is way unclear still and it's important to realize (as future copyright holders yourselves) what is legal and what isn't.
