Pandion is an open source instant messaging client for XMPP networks.
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RetroShare is a Open Source cross-platform, private and secure decentralised communication platform.
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qutIM is a free open-source multiprotocol ( ICQ, Jabber/ GTalk/Ya.
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Ayttm is an instant messaging (aka chat) client that provides all-in-one chat functionality for several major instant messaging services from one simple program.
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aMSN is a free open source MSN Messenger clone.
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Miranda IM is a multi-protocol instant messaging client for Windows.
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Smuxi is an irssi-inspired, flexible, user-friendly and cross-platform IRC client for sophisticated users.
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Pidgin is a chat program which lets you log in to accounts on multiple chat networks simultaneously.
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Empathy is a messaging program which supports text, voice, and video chat and file transfers over many different protocols.
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XChat is an IRC chat program for both Linux and Windows.
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emesene is a free Instant Messenger client for the Windows Live Messenger network.
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