This is an oddball, I know. But I can't see why this shouldn't work.
We are a mac household running 4 different Macs (including some older models).
G4 dual processor 1GHz with 2GB of RAM
G5 with 3GB RAM.
Both of these are running OSX 10.5.8 and using the "Other Platform" version of Minecraft (the Mac version appears to be Intel only).
A MacBook Air with OSX 10.7
Mac Mini (Intel) with OSX 10.8
These are running the regular Mac (Intel) version.
All of these have been updated since the 1.4.5 release.
Now, the G5 has no Airport card and is hard-jacked into the router. The other three are wifi, but that doesn't seem to affect which can see which. I have (pre 1.4.4) successfully LAN'ed the G4, the Air, and the Mini together in the past, but now it seems only the newer Macs (Mini & Air) can see each other. Even the G4 and G5 won't connect with each other (same OS, same version of Minecraft). Sometimes they just don't see the LAN world, and sometimes it's the "Connection Refused" error. I've shut off the firewall settings, so I don't think that's the trouble.
I'm not going to shell out a bunch of cash to replace the old Power PCs, since their only intended function is to let multiple people play Minecraft. Would running a server help? Any advice is appreciated.