The XMPP-Protocol (which is the official name of the “Jabber”-Protocol) is released under open source, Jabber itself has many advantages in comparison to other instant messaging protocols:
It’s open source
It’s based on plain-text, xml-style data
Everyone can set up a own Jabber-Server
It’s decentralized: There are now “central” servers
There are some implementation of this protocol for PHP:
XMPPHP (successor [...]
