The rules page doesn't seem clear, but I would be surprised if they don't allow the use of any free assets including sounds. Generally most Game Jams allow you to use anything that you have the legal rights to use, and anything that you either made during the jam or anything that is free to the public. (Ie, I can't use my own assets from previous games even though I have the legal rights, because they weren't available to the public.)
Anyway, I'm using a ton of Creative Commons sounds for mine