net-im/openfire is a java-based xmpp server with straightforward codebase. Decent for use in small environments.
I'm not using it anymore. It needs a revbump to 4.3.0. Which is a switch from self-contained ant-based build system to maven. If you are still using openfire it's your chance! Single public bug open related to parallel building: https://bugs.gentoo.org/639640 Likely will become obsolete with a switch to new build system. Good luck! -- Sergei