Hey I wanted to make sure if I am allowed to use stuff from your game (sounds) because I am making this game as a gamemode on garry's mod (garry's mod is a HL2 mod) (It's in lua btw).
I plan to enter a contest with it and one of the rule is "You must own the rights to all content in your gamemode" so I just wanted to make sure if I had the right to use those.
The main game package is open source, that does extend to the art assets therein. As long as you give proper credit as you mash them up, there's not going to be a problem. Files from separate moviepacks or moviesound packages don't fall under that rule, however, there you'd have to contact the creator.