"gr1d.org is a persistent multiplayer online programming game. Its inspired by games such as Robocode, Planetarion, various persistent online worlds and cyberpunk fiction.
"gr1d.org combines write-your-own code, persistent online world, cyberpunk-RPG, and multiplayer risk style domination and resource gathering together into a fun experience for programmers.
"As you gain levels, skills and experience, you can code more powerful agents to use these skills. You produce a fully-fledged class in the .NET ide of your choice, and upload it to the gr1d.
"While you're offline, your agents continue to run within the gr1d, looking for experience, resources and combat."
Continuation: Actually, I thought more about it, and I might have some possible solutions. It would probably change how the game works, though.
If unique players were separate processes altogether and they communicated with the server, then the game could support a plethora of languages because it could run each player as a separate process and link to it.
This seems incredibly dangerous for the server (running rogue programs), and annoying for players ("oh, sorry, your particular language isn't supported :/" or "oh sorry, the most recent version of your language isn't supported, even though you're using brand-new feature X"), but possible.
I've only use the c# variant of .net, but i'm under the impression that the framework itself is extremely language agnostic: http://en.wikipedia.org/wiki/List_of_CLI_languages
In fact, I believe you should be able to use Mono to develop for this using a fully-OSS stack. (I could be wrong)