jabberd 2.x project is the next generation of the jabberd project. It has been rewritten from the ground up to be scalable, architecturally sound and to support the latest XMPP Extension Protocols coming out of the XSF.
Please note : jabberd 2.x is not a newer version of jabberd 1.x but a completely different project.
Why XMPP ?
Extensible Messaging and Presence Protocol is an IETF accepted open Internet Standard for XML based communications technology.
It has been formalized under RFC 3920 and RFC 3921.
XMPP was designed for real-time communication, which powers a wide range of applications including instant messaging, presence, media negotiation, whiteboarding, collaboration, lightweight middleware, content syndication, EDI, RPC and more.... More Info »
The license under which the jabberd XMPP server is released is the GPLv2 from the Free Software Foundation.
This means (in short) that you are completely free to use, modify, distribute and even sell jabberd source and working installations.
For details see the General Public License v2 text.
For example Apple's ChatServer is a bit modified jabberd 2.1.
Source code : https://github.com/jabberd2