BZFlag is a 3D, multiplayer, tank battle zone, capture the flag game that pits players against each other in a networked environment. It runs on Windows 95/98/NT/2000, Linux, MacOS 10.x, Irix, Solaris, and others. An OpenGL accelerator is highly recommended, but it is playable with 3D in software.
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.
Chaotic Domain aims to revolutionize the RTS industry. Made up a team of "elite gamers" (not to mention great programmers and 3D modelers) we're combining the greatest features we like in other strategy games, fixes for some of the "annoying" parts of those games, and many new ideas of our own. With a full 3D galaxy that allows you to micro- or macro-manage and very customizable games, it should appeal to every user.
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.