Wikipedia
Tigase
Tigase is an open source ( AGPL3) project started by Artur Hefczyc in October 2004 to develop an XMPP server implementation in Java.
Initially the goal was to develop a fully compliant XMPP server with backward compatibility with an informal XMPP specification. In time the project has been split into smaller parts – server implementation, XML tools containing a parser for XML streams and a test suite with a built-in scripting language. In summer 2006, the client-side library and application in Java have joined the Tigase project. In November 2013, Tigase added a REST API layer project, and later HTTP tools and interface to the server program.
Tigase is currently in active development