Psi is the premiere Instant Messaging application designed for Microsoft Windows, Apple Mac OS X and GNU/Linux. Built upon an open protocol named Jabber, Psi is a fast and lightweight messaging client that utilises the best in open source technologies.
The goal of the Psi project is to create a powerful, yet easy-to-use Jabber/XMPP client that tries to strictly adhere to the XMPP drafts.and Jabber JEPs. This means that in most cases, Psi will not implement a feature unless there is an accepted standard for it in the Jabber community. Doing so ensures that Psi will be compatible, stable, and predictable, both from an end-user and developer standpoint.

Download : Psi Jabber 0.12 for Windows
Download : Psi Jabber 0.12 for MacOS
Download : Psi Jabber 0.12 for Linux