"Halo" is a word we just don't use on RPS. The last time it was tagged in a post was in 2009, and that was TF2. To find a time it was related to the game series you have to go back five years to 2008, and then it was to say that a cancelled, unannounced project was to have been a Halo MMO. In fact, we've never posted about a released Halo game, even if Kieron did post about a comic once. Which is to say, since 2004's Halo 2, Microsoft has made sure the series has had nothing to do with the PC. That's something a group of fans are now putting right, with Project Contingency.
As spotted by Kotaku, Project Contingency already has about 20 developers working on it. But they're after more. They say that they've released a very early work-in-progress trailer to try to lure more developers on board.
Slightly confusing is a conflict of information as to how much of Halo itself they're borrowing. The trailer begins saying that Halo assets are used under Microsoft's "Game Content Usage Rules", while their FAQ states, "All game assets are being made from scratch." It's relevant nitpicking, as you have to assume that Microsoft are already working out how to stamp this out of existence. The team have stated that it will be entirely free, and aren't accepting donations, which gives them some leverage, but just writing "Halo" on their webpage seems likely to cause trouble.
Built in CryEngine 3, the tech demo looks pretty enough. But obviously this is very early on, and they're avoiding discussions of a release date. But hopefully they'll be able to see this one through. If anything, they'll demonstrate to the goons at Microsoft that PC players are interested in buying their products, if only they'd let them.