Logging in to gaim has nothing to do with registering your distro - gaim is simply a client which allows access to various networks - AIM (Oscar and TOC protocols), ICQ, MSN Messenger, Yahoo, IRC, Jabber, Gadu-Gadu, and Zephyr networks. You just have to register a username with one of these networks to be able to use it.
As for peer-to-peer there are lots of great programmes for linux - limewire, gtk-gnutella, mldonkey. But my personal favourite is gift
it connects to fasttrack, openft, gnutella and opennapster networks and has several cool frontends.
I can't answer your question about registering red hat - I know nothing about it. It is linux, so I wouldn't have thought you needed to register it at all. Maybe red hat is special.