Bughouse can actually be played with 2N
players, with half the players on each team playing white and the other half black. If N
mod 2 == 1, then you have floor(n/2) playing white and N - floor(n/2) playing black, and vice versa on the opposite team.
Bughouse can also be played with an odd number of people if you play multiple rounds, by having one person wait out each round, and having the person who is checkmated switch with the waiting person at the beginning of the next game. Since bughouse tends to be fast-paced, this isn't too terribly dull for the person sitting out, and teams shuffle around a bit, which is kinda fun.