Open source Instant messaging

Corebird

Corebird is a modern, easy and fun Twitter client, just what you were looking for, right? (GPL)

Linux

Empathy

Empathy consists of a rich set of reusable instant messaging widgets, and a GNOME client using those widgets. (GPL)

Linux - FreeBSD

Gajim

The goal of Gajim is to provide a full featured and easy to use Jabber client. (GPL)

Linux - FreeBSD - Windows

HexChat

HexChat is an IRC client based on XChat, but unlike XChat it’s completely free for both Windows and Unix-like systems. (GPL)

Linux - Windows - MAC OS X

Instantbird

With Instantbird, we intend to redefine the way instant messaging is used, so that it works the way you want. Both simple and powerful, it will help you manage all your real time communications. (GPL)

Linux - Windows - MAC OS X

Jitsi

Jitsi (formerly SIP Communicator) is an audio/video and chat communicator that supports protocols such as SIP, XMPP/Jabber, AIM/ICQ, Windows Live, Yahoo! and many other useful features. (Apache)

Cross-platform

Konversation

Konversation is a graphical Internet Relay Chat client (IRC). (GPL)

Linux - FreeBSD

Miranda IM

Miranda IM is an open-source multi protocol instant messenger client for Microsoft Windows. (GPL)

Windows

Pidgin

Pidgin is a multi-protocol Instant Messaging client that allows you to use all of your IM accounts at once. (GPL)

Linux - FreeBSD - Windows

Spark

Spark is an Open Source, cross-platform IM client optimized for businesses and organizations. (GPL)

Linux - Windows - MAC OS X

10 applications