The basic problem with live jamming on the net is latency. You play along, hearing yourself in perfect timing, while the people receiving your music hear a delay, because of the time taken for the data to get from your computer to theirs. Unfortunately the delay is twice as big as that lag, because their
notes have to get from their PC to yours, and then your notes have to get all the way back again. Not conducive to good jamming.
How about using loops, then? Someone plays a 4-bar section, which everyone receives, along with the timing data. They begin jamming with a delay, and their sections are sent back again to the other player(s). Instead of attempting to play person B's notes with no lag, person A's software plays them at the beginning of the second loop. So the players can now play with no lag, and have their notes heard with no lag.
The price is that the leader has to change to the next pattern on their own.
Since people are receiving each other's notes with this fixed delay, I would expect a layering to happen - B harmonises to A, C to B, and so on. Each gets a different actual rendering of the music, since they are all synchronous with their own notes but offset with respect to everyone else's.
Would be a great experiment...