Joint Maneuvers is an open-source clone of the board game Diplomacy by Avalon Hill, set in space rather than Europe. It has a 3D (OpenGL) user interface, stunning graphics, a networked client-server architecture, and customizable XML maps.
You should go to the Sourceforge Joint Maneuvers project page and check it out, because there is some more information there.
Joint Maneuvers originated as a project for Brown University's CS032 course in Spring 2006, which teaches object-oriented design. The project was originally called "Diplomacy," and was mostly built within one month of turbo development as the final project. There are four original developers: Lincoln Quirk, Matthew Cannizzaro, Daniel Heller, and Daniel Winograd-Cort.
We got an A on the project. :) Once the semester was complete, we didn't want to see the project go to waste, so we decided to release it for your consumption on SourceForge.
Currently (Aug 19 2006), we've imported our Subversion repository and provided a big tarball (jointmaneuvers-0.1a) for you to potentially download. Now, I must admit, the svn and tarball are a real mess. The code itself is good, but I have a feeling that it's really really difficult to figure out how to build -- because not only do you have to unravel our mysterious build scripts, but you have to maybe even change some data directory in the source, or something. For this I apologize, and as soon as I get a few free hours, I will try to clean this up a lot.
Another concern I have is that we've stolen some images off Google Image Search and packaged them into the tarfile. (Mostly planet textures.) While I doubt anyone will come hunting, I still feel a bit uncomfortable with that, and I'd like to clean up a few licensing issues like that as well.
If you're brave enough to download it after all this, you're welcome to. Even if I don't have time to fix up the build scripts, I definitely DO have time to answer specific questions you have -- so email me (through sourceforge, lincolnq) or one of the other developers, and you'll get a response.