Allegiance: Free Online Multiplayer Game by Microsoft: Intro

Allegiance is an online game providing a mix of real-time strategy and player piloted space combat. Initially developed by Microsoft Research, the game was later released under a shared source license[1] and is now maintained/developed by volunteers. Gameplay relies heavily on good teamwork and forward thinking and players can fly a variety of craft, striving to destroy enemy team installations and protecting their own.

The game never achieved commercial success but it did manage to build a dedicated following, who have stayed with the game and continued its development. Due to the lack of commercial success, the official servers closed in 2002. As a consequence of this, the original retail version of the game is unusable. However, the Allegiance community has successfully rebuilt the game and it is now free to play.
Allegiance received GameSpot’s Best Game No One Played[2] award in 2000.