Opensource Messengers & Communication Clients

Adium - Mac OS X open source instant messaging client that aggregates the popular IM networks.

aMSN - MSN Messenger's open source clone for Linux users.

Ayttm - Ayttm is an instant messaging client with all-in-one chat functionality for major instant messaging services.

Coccinella - A Jabber client with integrated whiteboard features; includes features like file transfer, multi-user chat etc.

Kopete - Part of KDE desktop; a wonderful instant messaging application with voice and video capabilities.

Gaim - A very flexible instant messaging application compatible with Linux and Windows offering support for AIM, ICQ, MSN, Yahoo and others.

Ineen - Ineen is a feature loaded open source audio and video conferencing desktop tool.

IRSIM - Uses PHP and mySQL and provides interaction with multiple messaging clients.

Java Jabber Server - A nice open source Java implementation of Jabber instant messenger.

Kopete - Kopete is a flexible instant messenger and multi protocol system with support for AIM, Yahoo, IRC and MSN.

Licq - A C++ based multi-threaded ICQ clone; uses an extensive plug-in system.

MIMP - Mobile version of IMP; functionality includes mailbox viewing, message viewing, deletion or composition of new messages.

Miranda IM - Fast and handy multi-protocol messenger for Windows.

Openfire & Spark - Real time cross-platform IM client and server based on Jabber protocol.

Pidgin - Covers multiple protocols including AIM, ICQ, MSN, IRC, Jabber etc.

PlanetaMessenger.org - Java based open source instant messenger offering plug-in support for various IM networks.

Psi-im - An open source instant messaging client developed for Jabber. Has communication capabilities with AIM, MSN and ICQ etc.

SIM-IM (SIM Instant Messenger) - Free software package providing plug-in based messaging with support for various protocols.

Spark - Open source instant messenger with integrated support for group chat, telephony and security.

TjK - A portal based open source version of AOL Instant Messenger, originally developed for UNIX users.

Tkabber - Open source client for Jabber instant messaging and works on many platforms e.g. Linux, Windows and Mac etc.

WengoPhone - WengoPhone is a popular VOIP soft-phone client for making free PC-to-PC calls over the internet.

XChat - An IRC chat client for both Windows and Linux.

Yafumato Web Messenger - A web-based open source client allowing users to connect to AIM, Gtalk, MSN and Yahoo.