so basically

I'm rewriting Quake 3
@a1ba how did you get to that? 
@steffo well, not literally, but...

My assumption is that Ritual received Quake 3 source code at the end of 1999, not too long before it's release. fakk2-sdk hints at it as all files have short changelog at the beginning with the exact dates. The engine functions also appear to be different from Quake 3 Arena source code, but that's probably because Q3A had tons of updates before the source code release in 2005. It also has random Quake 2 (?) leftovers.
@steffo it's just easier for me to check and rewrite every function instead of shaping Q3A into something that it was 5-6 years before the source code release.

For the same reason, ioq3 with 20 years of community patches is nearly useless for me at this stage. Might be useful in the future though.