I can't help you with the first question (you may have to ask on the TG forums), but to the second question: Some "tester" leaked the unfinished mod so it ended up on the internet and the third question: I don't *think* it changes anything, since they are not modifying and of the game engine code, only the assets. If your game already works, it is likely to continue working on Vista and vice versa.
Oh, and welcome