The rules say we have to make all assets from scratch. But I´m still curious if this is allowed or if it is part of the challenge.

Yes, that's fine. I'll clarify that rule; I can consider downloading royalty free music/sound effects "making" them :p. Music and sound effects are particularly hard, and the idea of this jam is to have fun, so I won't make any overly strict restrictions.

Making art is easy (in terms of getting programs to do so), so that still has to be original!