UPDATE: NOW WORKS ON LINUX! (Thanks IsharaComix!!!)
I've spent the past few years building a free open-source online strategy game called Strategic Initiative.http://www.strategicinitiative.org
We have an active player community and always welcome newcomers! It's a game of exploration, conquest, and technology advancement played over 10 days. I don't know what you call that genre; "slow real-time"? The economy is super-simple--the only commodity is city-time for building new units. All the complexity has been focused on tactical unit engagement: naval, land, air, missiles, supply, interdiction. It's a lot of fun!
The game is loosely based on a GNU online multiplayer game called Empire that I lead for a few years back in the 90s. I also did a lot of LPMUD coding back in the day...
The license is GNU GPLv3. Here's a screenshot of what the map looks like in the game.
Would love to see some new players, and would especially love help with the build for Mac & Linux!