they both can draw on the screen at the same time... thats why its so amazing :D
Here's a link to the mutiplayer thread with the script... just for anyone who is passing by ;)
Multiplayer will mean that you can build stuff together - or if more game modes are added - play in teams.
For example, Lemmings mode. The most difficult part will be the client sync as the state would need to be sent between the instances, either throught updates, modifications, or whole scene.
Depending on how it's done, and a future multicore approach, this could even include some sort of distributed processing - that would be awesome, imagine 1920x1080 ie. around 2 000 000 particles running at 60fps+