Morpheus is now based on Gnutella as well (they switched from Fastrack quite a while back). Hence it will yield about the same things as Limewire or any other Gnutella client. Edonkey is a bit of a hassle on the Linux platform but it does work. Kazza is/was available for Linux, but I never could get it to work. AFAIK, your best bet on Linux is the Gnutella network (as much as it sucks). Hopefully we'll get a better scaling P2P technology soon (open source so that we get clients on all platforms).