You will need to have GNU Pth 1.2 or newer installed on your system before starting: http://www.gnu.org/software/pth/.
Download 0.8.1, run "./configure && make && make install". This is a core library for all server-side Jabber components. All problems/comments/patches go to lib-dev@jabber.org. Watch the lib.jabber.org team site for updates or join the team to help out.
Download 0.8.1, run "./configure && make && make install". This is a server-side XML middleware application for Jabber. All problems/comments/patches go to etherx-dev@jabber.org. Watch the etherx.jabber.org team site for updates or join the team to help out.
Download 0.8.1, run "./configure && make && make install". This is the Jabber server. All problems/comments/patches go to server-dev@jabber.org. Watch the server.jabber.org team site for updates or join the team to help out.
Documentation can be found at docs.jabber.org, start with the Introduction/QuickStart section and go from there.
After you have it installed, start the server by running "etherxd" which will load jserver and start listening on port 5222. Use the protocol and build a client or use one of the existing clients.
If you have problems with any component, please send it to the correct team. If you have overall problems, please join the developers on IRC (irc.openprojects.net) in #jabber or send a report to the bugs@jabber.org.
If you have any further general questions or comments about Jabber, feel free to e-mail us at info@jabber.org.