I make my own music and I want to use some of my old music for the soundtrack. I just realised this may not be allowed, but there are no clear rules for this. I already have some original tracks for my game so it's no big deal if it's not.
I think that any assets you use for the game that you didn't create during the jam have to be freely available to everyone. Unless you make them freely available for people to use going forward, I don't think your use of them would be legit.
I sympathize with you because I have some old music I made that I would use if I could.
