Freeciv is a multiuser reimplementation for Unix/X of the famous Microprose game of Civilization. By default, the game is an improved Civ II, but this can be customized; modpacks for near-100% compatibility with Civ I and Civ II are included. Multiuser gameplay is real-time: in each turn, all human players move concurrently. The game is designed to remain fairly playable even on poor network connections. Freeciv can also be played on standalone machines, and its AI players are a good challenge for beginners. The source code comes with the server, two X clients, and non-X clients for MS Windows and Amiga. Freeciv is released under the GNU General Public License. It is maintained by an international team of coders and enthusiasts, and is easily one of the most fun and addictive network games out there.
XBoard is a graphical chessboard for X that can serve as a user interface to play against any of a variety of chess engines that run on your local machine, or against human or computer opponents on an Internet chess server. XBoard can also be used by itself to read and write game files in PGN (portable game notation). WinBoard is a port of XBoard to Microsoft Win32.
Crimson Fields is a tactical war game in the tradition of Battle Isle. Mission objectives range from defending strategically vital locations to simply destroying all enemy forces in the area. Tools are available to create custom maps and campaigns. The original Battle Isle maps can be played if the player has a copy of the game files.
Empire is a game that is played against human opponents over a computer network. It is possible for a game to last from a few hours to many months. While the common goal of an Empire player is to win, there is no clear-cut definition of what winning is. Players may seek to achieve whatever goals they want to achieve.