Copyright Question

[Cranky Old Man]

Hey there all. Here's more of a legal question. Am I allowed to use other people's assets, and/or music in my work if I give them credit, and don't make profits out of it?

What I have in mind goes beyond simple community work, I'm talking even to the boundaries of big-budget movie official soundtracks. Am I allowed to use those as long as credit is given, and I don't make profits out of it? Or is it still considered a violation of copyright?

Reason I'm asking is that I'd hate to submit my mod to Moddb someday, and have removed for reasons like this one.

That can depends on what sort of licence the song is released under, but record company songs are typically guarded very diligently, because every copy of a song is worth the price of a CD, meaning that your game will be worth the price of a CD times the number of downloads. If your story happens to become popular for some reason, and the company wants 10% of the download revenues, then that's a lot of money, and you're not even selling the story.
If you really want that particular song on your story, then theoretically the way to go is to ask the record company or maybe the artist, if you can use it for your story, preferably free of charge. I have a feeling they'll turn you down, but that's the way to go.
I'm not certain if the same goes for covers of the same song, though. If a small artist makes a MIDI/mod song cover of the song, then I think his copy HAS to be free, because he can't make money from the original unless he asks permission. Just make sure to credit him too.