You can use the JRE 1.4 for LimeWire, but remember, currently LimeWire has to compatible with the old JRE 1.1.8 so it works on MacOS.

I think the LimeWire developers are already working on Skins.

Building communities on top of the Gnutella protocol is quite difficult due to its decentralized nature.

For IRC chat, use an IRC client. Improved Instant Messaging features would be nice, - but LimeWire is a file-sharing tool. I don't think it has to be one of those all in one programs, that can do a little of everything but nothing properly.