Many game magazines have praised Halo as one of the best and most important games of all time. The game's popularity has led to labels such as "Halo clone" and "Halo killer", applied respectively to games either similar to or anticipated to be better than it. In addition, the game inspired and was used in the fan-created Red vs. Blue video series, which is credited as the "first big success" of machinima — the technique of using real-time 3D engines, often from video games, to create animated films.

In celebration of these accomplishments Microsoft has decided to release the source code of Halo Combat Evolved under GPL v3.

Microsoft thinks its high time some quality open source games are released noting a significant hole in the Linux Gaming market. "We see it as a great opportunity to introduce Linux users to Microsoft products."