LimeWire is one of the few Gnutella clients (besides Phex AFAIK) available for Mac, yes. For other operating systems there are many more gnutella clients. Xolox, BearShare and Gnucleus for windows or gtk-gnutella, mutella, qtella for linux for example.

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Morgens ess ich Cornflakes und abends ess ich Brot
Und wenn ich lang genug gelebt hab, dann sterb ich und bin tot

--Fischmob