A release party. It's someone people throw when they release some form of work (Such as a book, movie, CD, etc.) and people/fans come to hang out. Release parties are thrown generally as soon as the item is released.
In this case, I would release BSoaKFF, and everyone who downloaded it would go play it on KSO. There is definitely enough space for hundreds of people to run around in the level, and the way its set up so even if someone completes a certain part of the level, you still have to complete it as well.