You are always the owner of the game you make for a jam.
No jam would ever want to take this privilege away from you for one simple reason. If you take all the rights to the software you also inherit all the responsibility. This means that if someone here was to make a timebomb that goes off in one month and either the giftee or the jam organizers took the rights to the software they would be legally responsible for the damages. That's not a risk that jam organizers want to take, so they usually say something like: "Anything you make during the jam is your property. We claim no rights or ownership of your game".