Wikipedia
ejabberd is an XMPP application server, written mainly in the Erlang programming language. It can run under several Unix-like operating systems such as Mac OS X, GNU/ Linux, FreeBSD, NetBSD, OpenBSD and OpenSolaris. Additionally, ejabberd can run under Microsoft Windows. The name ejabberd stands for Erlang Jabber Daemon (Jabber being a former name for XMPP) and is written in lowercase only, as is common for daemon software.
ejabberd is free software, distributed under the terms of the GNU General Public License. , it is one of the most popular open source applications written in Erlang. XMPP: The Definitive Guide ( O'Reilly Media, 2009) praised ejabberd for its scalability and clustering feature, at the same time pointing out that being written in Erlang is a potential acceptance issue for users and contributors. The software's creator, Alexey Shchepin was awarded the Erlang User of the Year award at the 2006 Erlang user conference.
ejabberd has a number of notable deployments, IETF Groupchat Service, BBC Radio LiveText, Nokia's Ovi, KDE Talk and one in development at Facebook. ejabberd is the most popular server among smaller XMPP-powered sites that register on xmpp.org.
With the next major release after version 2 (previously called ejabberd 3), the versioning scheme was changed to reflect release dates as "Year.Month-Revision" (starting with 13.04-beta1). It was also announced that further development will be split into an "ejabberd Community Server" and an "ejabberd Commercial Edition [which] targets carriers, websites, service providers, large corporations, universities, game companies, that need high level of commitment from ProcessOne, stability and performance and a unique set of features to run their business successfully."