[EricH]

Originally Posted by slent thndr

It has its wheels laid out as northwest, northeast, southwest, and southeast, and northward motion involves all 4 wheels spinning forward. Having the northwest and southeast motors on, and the northeast and southwest motors motionless would produce northeasternward motion.

I suppose that there are just two ways to set up a 4 wheel omnidrive?

Yes, there are only two ways (as long as you are using only standard omni wheels--if you go nonstandard, who knows how many ways there are).
As for the robot in the video: the control is similar, but: to go north, all four go one way, south, all four go the other way. East or west, two go one way and two go the other way. To turn, all the motors spin like they were trying to spin the same turret (assuming it's a circle laid on top).