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.
FMG is a futuristic war game based on full metal planet (an 'old' board game) and playable in a Web browser. Land your spaceship on Full Metal Planet, pick up ore, destroy or capture the enemy expensive hardware, and if you can, capture their own freighter with a hold full to bursting. Each game is independent. Although it is playable in English, not everything in the guide is translated yet.
G2F3 (Generic Game Framework in eiFFel) aims to simplify the development of two player zero sum strategy games by separating game specific code from reusable generic code. So far, abstract board games are best supported. This software is written using GNU SmartEiffel. The package comes with six example games.