Here's what he posted over on Func_Msgboard:
Should be standard engine feature in a few weeks. It's very prototype at the moment.
/Fifth is largely to blame.
Read the names of the players in the scoreboard.
If he gets multiple gamepad support spliced in, one could hook up their computer to a TV and play couch-coop, split screen Quake. I hope it will also support connecting all the extra players to the same online server (that server being FvF, of course!)....