This news is sure to warm the hearts of many old-school Mac gamers: Bungie Software’s legendary first-person shooter Marathon series has been rebuilt using a new game engine and re-released for free. They’re available for Mac OS X, of course, along with Linux and Windows.

Before Myth, before Halo, Bungie earned a place of honor in the pantheon of great game developers when it introduced Marathon, a first-person shooter that came out on the Mac. The game series was innovative for its time, featuring network play, advanced physics and Bungie’s legendary attention to detail and immersive storyline.

The game engine making it possible is Aleph One, an open source project that combines the Marathon game code with a modern OpenGL shader, Internet-based multiplayer support, modern mouse look and gamepad support and plug-in support for future modifications. Aleph One’s development has carried on for 12 years, and the Aleph One development community is celebrating the milestone with this release, which incorporates all three Marathon games: Marathon, Marathon 2: Durandal and Marathon Infinity.

Marathon now has a modern Heads Up Display (HUD), high resolution graphics and extensive changes to the game scenario. Marathon 2 gets the high-resolution graphics that were previously only available in the Xbox Live Arcade release of the game. And Marathon Infinity also gets a high-res overhaul.

The Marathon Open Source repository also makes many third-party scenarios and network maps available for download.