Für MacOSX users there is no solche alternative. At least none that ich would recommend.

Phex works on MacOSX but it's java too and LimeWire is the more feature rich client. There are Acquisition and Acqlite, the former allegedly violates the GPL, the later is not maintained anymore and both of them are based on LimeWire.

There is Poison which connects to the Fasttrack network but I'd say LimeWire is better (still, you might want to try that). On windows or linux there would be some alternatives but not for OSX unless you manage to compile gtk-gnutella under OSX.