The Marathon Open Source Project. Perhaps more complicated than I thought. I think the chronology is:

  • Marathon released on Mac, 1994
  • Marathon 2 released on Mac, using a different game engine, 1995
  • Bungie release the source code for M2’s game engine, 1999
  • Aleph 1 released, a new game engine based on Bungie’s source code
  • M1A1 uses Aleph 1 game engine but the original Marathon texture files etc, 2002
  • Whole thing gets ported to Windows.
  • Bungie make whole trilogy available as freeware, 2004

Hmm. Aleph One actually is better code than the original, as it includes loads of enhancements, as Wikipedia points out:

“A number of aesthetic additions to Marathon Infinity have been developed. In early 2000, OpenGL rendering support was added, which at the preference of the user could smooth walls, landscapes, monsters, items and weapons to give them less of a pixelated appearance. Additional features using OpenGL include translucent media (allowing for translucent liquids) and colored fog. As time progressed, anisotropic filtering replaced smoothing and the addition of z-buffer increased game performance. Aleph One supports higher screen resolutions than Marathon Infinity and can use external background tracks in MP3 format. Though not heavily emphasized, there is support for three-dimensional models.

Though many of the changes are sensory, some involve greater engine capabilities. More than twice as many polygons can be drawn on the screen at a single time as Marathon Infinity and viewing distances can be far larger. Lighting effects can be more advanced and more polygons with transparent edges can be viewed in a single frame, allowing for structures such as pyramids and incredibly tall staircases. Though it is currently not supported, early versions of Aleph One were able to accomplish truly three-dimensional polygons, allowing for real bridges and balconies as opposed to just creating illusory 3D with overlapping polygons.The maximum number of creatures a level can hold is three hundred and the sprite-drawing capabilities of Aleph One are far superior to those of Marathon Infinity. Controls have been slightly expanded as well. Aleph One has an option that allows interchanged running and walking, as well as sinking and swimming in liquids. The mouse can be used more effectively and its sensitivity can be set. If desired, weapon switching may be disabled.”

Marathon Markup Language

Wikipedia again: “In 2000, support for a markup language which would eventually be called the Marathon Markup Language or MML for short was added. MML files can set things such as file names, weapons order, the colors of the automap feature, transparency of certain sprites and other things. One of the most frequent uses of this language is for installing high-resolution wall and weapon textures for play.”

AA: is Aleph one actually an emulation, then?