Wait, where does this come from? FreeDoom is just a remake of the Doom assets that are allowed to be used by anyone who doesn't own the full game.
I do know that the Hyper3DGE engine that Chillywilly was working on for the team behind Hypertension released a version with FreeDoom around 2008 I believe. Is that what you were referring to?
This is the same engine that Hypertension uses, just super early and hasn't been updated publicly in over a decade. The source they use for their game has been further updated since then. Other people would release mods with this engine and make more games, but the older release lacks sound I believe so nobody ever used it in any projects for that reason alone. Maybe somebody could update the source so we could use the enhancements this engine has?
https://sourceforge.net/projects/edge2/
The feature list is pretty extensive!
As a continuation of the EDGE Project, hyper3DGE gives the end-user more power from the most advanced alternative DOOM engine - combined with portability to most systems, including game consoles.
Features
Uncapped OpenGL 2.0 rendering with support for Quake 2, Quake 3, DOOM 3, and Half-Life Models.
Splitscreen local networking for cooperative, deathmatch, and botmatch play.
Sega Dreamcast portability (currently under /source).
Powerful DDF, RTS, and COAL scripting to make your Doom mods come to life.
Now Supports Heretic, Chex Quest, and Hacx.
Advanced rendering effects, such as normal maps and dynamic shadows
Custom Level Editing program, 3DGE Builder, tailored specifically for 3DGE!