NStars is a project to clone the popular Stars! game in C#/.NET, as well as to provide tools that aid in the playing of Stars!. Currently, it is is very preliminary and it most likely will not be complete for a long while.
NStars eventually hopes to:
Being written in C#/.NET, NStars requires the .NET framework to be installed, which of course is currently only on Windows. Hopefully in the future, Mono will take care of that.
NStars is currently in version 0.4. Pretty much, one can start a single player game and build factories, mines and defenses. Even this is not fully implemented. My next milestone is to have an almost "playable" multiplayer, where one can just build factories, mines, and defenses.
SourceForge project page
A new game
Race creation wizard
Viewing a *.map/*.pla file combination of an existing game