Pidgin is an instant messaging program for Windows, Linux, BSD, and other Unixes. You can talk to your friends using AIM, ICQ, Jabber/XMPP, MSN Messenger, Yahoo!, Bonjour, Gadu-Gadu, IRC, Novell GroupWise Messenger, QQ, Lotus Sametime, SILC, SIMPLE, and Zephyr.
Pidgin can log in to multiple accounts on multiple IM networks simultaneously. This means that you can be chatting with friends on AIM, talking to a friend on Yahoo Messenger, and sitting in an IRC channel all at the same time.
Unified OS X instant messaging platform
Kopete is a flexible and extendable multiple protocol instant messaging system designed as a plugin-based system. All protocols are plugins and allow modular installation, configuration, and usage without the main application knowing anything about the plugin being loaded. The goal of Kopete is to provide users with a standard and easy to use interface between all of their instant messaging systems, but at the same time also providing developers with the ease of writing plugins to support a new ...
Psi is a leading instant messaging / real-time communications client for the Jabber network (using the XMPP protocol). It is cross platform, available for Windows, Mac OS X and X11 (Linux, BSD, Solaris etc.) platforms. It uses the Qt library.
It aims to be (and is famous for being) standards compliant and stable. It is also at the cutting edge of XMPP development, with several of the authors very actively involved in the XMPP standards extension process.
Miranda is the next generation Miranda IM client for Windows.
The goal of Gajim is to provide a full featured and easy to use Jabber client. Gajim works nicely with GNOME, but does not require it to run.
Openfire (formerly Wildfire) is a real-time collaboration (RTC) server dual-licensed under the Open Source GPL and commercially. It supports instant messaging, group chat, and VoIP and uses the only widely adopted open protocol for RTC, XMPP (also called Jabber). Openfire is incredibly easy to setup and adminster, but offers rock-solid security and performance.
Use Openfire in your organization as a more secure and feature-rich alternative to the consumer IM networks. Or, replace your exis...
ejabberd is an instant messaging server written in Erlang. ejabberd is cross-platform, distributed, fault-tolerant, and based on open standards to achieve real-time communication (Jabber/XMPP).
A chat network to IRC gateway. Currently supports Jabber, MSN, OSCAR (AIM/ICQ) and Yahoo protocols.
A Jabber/XMPP connection manager, this handles single and multi user chats and voice/video calls.
Smack is an Open Source XMPP (Jabber) client library for instant messaging and presence. A pure Java library, it can be embedded into your applications to create anything from a full XMPP client to simple XMPP integrations such as sending notification messages.
Spark is an Open Source, cross-platform IM client optimized for businesses and organizations. It features built-in support for group chat, telephony integration, and strong security. It also offers a great end-user experience with features like in-line spell checking, group chat room bookmarks, and tabbed conversations.
Combined with the Wildfire server, Spark is the easiest and best alternative to using un-secure public IM networks.
ECF is a framework for building communications functions into Eclipse-based tools and applications. It can be used to create other plugins, tools, or full applications that require asynchronous point-to-point or publish-and-subscribe messaging.
ECF is also a small set of applications for real-time developer communication, including instant messaging, file sharing, and real-time collaboration.
An XMPP server.
jabberd 2.x series is the next generation of the Jabber/XMPP server.
It has been rewritten from the ground up to be scalable, architecturally sound and to support the latest protocol extensions coming out of the XSF.
Note that jabberd2 is NOT a new version of jabberd14. It's a different project with distinct codebase and features.
Tsung is an open-source multi-protocol distributed load testing tool. It is protocol-independent and can currently be used to stress test HTTP, SOAP PostgreSQL, and Jabber servers.
Tigase Jabber/XMPP Server is Open Source and Free (GPLv3) Java server using all available features in last JDKs. It uses NIO for network communication, selectors, concurrent JDK framework, security library and so on. All these functionalities are available directly from JDK so the need for external libraries is limited to minimum. Actually it doesn't use any external library at run-time. A few third-party libraries are used for development such as JUnit, Forrest, UnitTestsGen and ANT
SIP Communicator is an audio/video Internet phone and instant messenger that supports some of the most popular instant messaging and telephony protocols such as SIP, Jabber, AIM/ICQ, MSN, Yahoo! Messenger, RSS, IRC and soon others like IAX.
Plugin based multi-IM communicator. ncurses or gtk2 (in progress) based GUI.
Support for different protocols: irc, jabber (including gmail), gg (gadu-gadu largest polish IM), tlen, nntp (read only).
PyICQt is an ICQ transport written for XMPP/Jabber written in Python/Twisted. It provides a mechanism for XMPP users to log in to their ICQ accounts and communicate with friends from ICQ.
Citadel is a highly integrated Groupware Platform with a Web 2.0 enabled Web interface, but also providing SMTP, IMAP, POP3 and GroupDAV access to its content.
Citadel offers Versatile email services with very low administration needed. It provides its own implementations of these server protocols:
Imap, Pop3, SMTP, ManageSieve, Citadel.