In case things don't update, the main page and discord channel, are updated with the theme for the jam:

The theme for our first game jam is: Opposite Day: Your challenge is to take a game mechanic/system, or genre qualifier -- something that is considered vital when defining a game, and do the opposite of it. This doesn't mean creating a bad or janky version of that genre, but to do something that would be the opposite of what we would normally expect out of this gameplay loop.