Hi!
No, there isn't a prize for the winner. The jam is just a way to dedicate some time to make something and share it with others, and get motivated by others' works during the process. There isn't even any voting happening at the end of the jam, just
- put your game online
- try the games of the other participants
- enjoy your time :)
Just so I can weigh the possibilities of having a prize for a possible future jam, what would you expect / why would you expect a prize exactly, if you don't mind telling me? I'm really just being curious :)