The best open source alternative to Sim-IM is Thunderbird. If that doesn't suit you, our users have ranked more than 25 alternatives to Sim-IM and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Sim-IM are Pidgin, Adium, Franz and Psi XMPP Client.
Cross-platform email client supporting multiple identities, chat, and strong filtering. Extend functionality with add-ons like RSS/Atom feed readers and PGP support.
Pidgin is a chat program which lets you log into accounts on multiple chat networks simultaneously. This means that you can be chatting with friends on XMPP and sitting in an IRC channel at the same time.
Adium is a free and open source instant messaging application for Mac OS X, written using Mac OS Xs Cocoa API, released under the GNU GPL and developed by the Adium team. Based on the libpurple protocol library, Adium can connect you to any number of messaging accounts on any...
Centralize multiple chat and messaging services in one customizable interface, organize workspaces, receive synchronized notifications, manage multiple accounts per service, and easily access popular platforms on Mac, Windows, and Linux. Privacy controls included.
Feature-rich XMPP client for advanced users offering strong customization options, secure encrypted messaging (TLS, OpenPGP, OTR, OMEMO), file transfers, audio/video calls, support for animated emoticons, modern themes, group messaging, and multi-platform compatibility.
Empathy is a messaging program which supports text, voice, video chat, and file transfers over many different protocols. You can tell it about your accounts on all those services and do all your chatting within one application.
Kaidan is a simple, user-friendly Jabber/XMPP client providing a modern user interface using Kirigami and QtQuick. The back-end of Kaidan is written in C++ using the QXmpp XMPP client library and Qt 5.
Kopete is an instant messenger supporting AIM, ICQ, Jabber, Gadu-Gadu, Novell GroupWise Messenger, and more. It is designed to be a flexible and extensible multi-protocol system suitable for personal and enterprise use.
Instantbird is an instant messaging client based on Mozilla XULRunner and the open source library libpurple created by the software developers of Pidgin . Over 250 add-ons allow user customization of, and addition of, features.
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...
Finch is a console-based IM program that lets you sign on to AIM, Jabber, MSN, IRC, Yahoo!, and other IM networks. It runs on Unixes. It uses GLib and ncurses.
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