GlDoom

glDoom (created and maintained by Bruce Lewis), based on WinDoom, was the first source port to add support to Doom. Before beta testing could be completed and the source code released publicly, the source was lost to a hard drive issue. The last official glDoom version was released on December 23, 1998.

In April 2010, glDoom reappeared on SourceForge. The author discovered copies of the source code on the computer of a late friend of his. This resurrected version of the source code, however, was probably not the latest version (some features which work in the released binary no longer did) and had to be updated to compile with newer development environments. The ninth and last update to its SVN repository was made on October 8, 2010. This is known as v0.95a.

2020 unofficial updates
In April 2020, precisely ten years after glDoom resurfaced on SourceForge, unofficial updates to the latest glDoom code appeared, created by a programmer called Vsevolod Popov, aka RedPowar. He released 0.95b on April 4, and 0.95c on April 8, 2020. They contain several improvements to the port:
 * New floor/ceiling generation code (derived from Doom Legacy)
 * Aspect ratio fix (correct rendering on 16:9 displays). glDoom can now render for example in 1920x1080p resolution properly
 * Fixed invisible area culling (behind walls in sectors without ceiling)
 * Few bugfixes for buffer overflows & invalid memory pointers