It does not say anywhere that this is a closed jam, but the brief description does currently say the following:
You'll be tasked to create a JAM based around or in Hell. The
class will then vote on which of the JAMS submitted will be the best. Good luck and have fun!
This makes me wonder, who are the members of this "class". Sounds a bit like it's a jam organised by some game dev school by and/or for the students of that school. It could also be a particular social class (like the proletariate) or an MMORPG class (like a Shaman), but some how I doubt thath.