No restrictions. There is also a junior category being planned, but it seems unlikely to get ready in time for this year, because of the special arrangements it requires - for the entrants to prove their ages, for example.
I'm not part of the jury who decide the winners, and those decisions are made in October, so you'll have to wait until then to know. Some games may also be picked up for the weekly polls where people can vote their favourite, but that may not be always based on how good the game is.
