When you have two controllers hooked up to one computer it is split screen. You can choose to split of horizontally or vertically. I have run two on my box, one using the provided dongle and my transmitter and the other using my USB Real Flight G2 controller. It works really well. I like doing a slow harrier with the smoke on and blocking my friends view...

If you want to run it on two different computers simultaneously you are going to need another copy of the software/dongle combo.

scott.