Freeciv was inspired by one of my favorite computer games, Civilization.
For those unfamiliar with this game, it is a strategy game where your objective is to manage a civilization from its birth until world domination (through military or cultural advancements). You can play against the computer or multiplayer through the net.
Freeciv has a bunch of maps and scenarios already loaded in it, and dozens of units (some I hadn’t even found on the proprietary Civilization).
This is a pretty active open source project, being translated in well over 20 languages and it runs on Windows, Linux, and MacOS X.
Let’s heard it from you, does it stand up to the proprietary Civilization?