I'm on a mac, meaning I can't use kazaa, which doesn't work on our college network well anyways. Gnucleous has been working very well for others, but I haven't been able to find a similar LAN-focused system for mac. Is there one out? Is one being developed? Please?

You can try LimeWire, Mactella, QTella or Napshare.
I would recommend LimeWire though because it is the most advanced of those mentioned above.

or even MacPhex

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Het algemeen gnutella forum in Nederlands

I should have been more clear, none of the normal gnutella programs work on our network, but the LAN version of gnucleous does. Is there any mac program that will do this too?

Actually there is no difference between Lan and Internet,
the Lan is just smaller and most computers are supposed to have a fixed IP. In the Gnucleus Lan version there is that IRC stuff implemented but you can run a small GNet within a network.

Have you tried LimeWire already?

If you can't connect, try getting the IP of someone on your LAN who is connected with Gnucleus. Connect to that address manually and after that point it should work automatically.