They are all on the same network. All three are based on the FastTrack P2P Stack. There is some licensing dispute right now, so the Kazaa people who created FastTrack activated some code that is disabling Morpheus clients out there and not allowing them to access the FastTrack network. Morpheus is supposedly working on getting a gnutella client out soon.
I think the morpheus people must have known that this was going to happen for a while now which is why they almost have a gnutella version ready.