Can i get banned from Garry's Mod somehow, if i use leaks?

Garry's Mod hasn't had any game ban records as far as I've known, and there's almost no way to actually get banned from the game iirc.

If you purchase these scripts yourself and leak them, You're account could get terminated but otherwise you're in the complete clear.

Watch and Inspect anything you download for backdoors, however. Their usually kept in the lua/autorun section.