In a similar spirit to Freedoom, for Quake fans perhaps you'll want to take a look at LibreQuake, which aims to do a similar thing to allow you to play Quake content with completely open source software.
All of the Quake data files remain copyrighted and licensed under the
original terms, so you cannot redistribute data from the original game, but if
you do a true total conversion, you can create a standalone game based on
this code.
As I understand it the engine is Foss but the assets aren’t, like the doom engine vs the doom wad.
Isn’t Quake already open source?
As I understand it the engine is Foss but the assets aren’t, like the doom engine vs the doom wad.
So I would presume this libre alternative would have all the assets free, no?
According to their GitHub the art is BSD licensed and the rest GPL