As the comm's name implies, it's for threesomes.
Prompting is until September 30th and you can submit prompts here. The only rule is that RPF/RPS is not accepted. :)
The prompt list will be posted on October 3rd, when claiming can begin. There's no limit to the amount of people that can claim one prompt so don't worry! Fics can be posted until Jan 3rd, so people have quite a while.
So go submit a few if this interests you! Looks fun! :)