Open Source Operating System

ReactOS is an open source computer operating system intended to be binary compatible with application software and device drivers made for Microsoft Windows NT versions 5.x and up (Windows 2000 and its successors). A spin-off of a previous attempt to clone Windows 95, development started in early 1998, and has continued with the incremental addition of features already found in Windows.

Ope Source Operating System

FreeDOS (formerly Free-DOS and PD-DOS, often abbreviated to FD or FDOS) is an operating system for IBM PC compatible computers. FreeDOS is made up of many different, separate programs that act as "packages" to the overall FreeDOS Project. As a member of the DOS family, it provides mainly disk access through its kernel, and partial memory management, but no default GUI (although OpenGEM is listed on the official FreeDOS website).

Adium - IM Client for Mac

Open Source Instant messaging Client

Adium is a open source instant messaging client for Mac OS X that supports multiple IM networks, including Windows Live Messenger, Yahoo! Messenger, Google Talk, AIM, ICQ, XMPP and OTR. It supports many protocols through the libraries libezv (for Bonjour), MGTwitterEngine (for Twitter), and libpurple (for all other protocols). It is written using Mac OS X's Cocoa API, and it is released under the GNU General Public License and many other licenses for components that are distributed with Adium.

Spark - Open Source IM

Open Source IM Client

Spark is a secure, fast, Open Source, cross-platform IM client optimized for businesses and organizations. It features built-in support for group chat, telephony integration, and powerful security. It also offers a outstanding end-user experience with features like in-line spell checking, group chat room bookmarks, and tabbed conversations.