The Machine Games (mg1 & dopa) FGDs were shared with the community in the Quake Mapping Discord.

the quake_mg_trenchbroom_ericw fgd is the main one we used. The others get loaded in as sub-fgds

Also there is test_shadow.map in Quake/rerelease/id1/pak0.pak 

From a legal standpoint reverse-engineering is totally fine (decompiling = reverse-engineering btw)

https://www.law.cornell.edu/wex/reverse_engineering

What you *do* with the decompiled code could be a different story. But hey. Most, if not all, Quake mods derive heavily from copyrighted work already. Should we all just stop making mods because we're building them off of other people's work? Without explicit permission?

I don't really see the moral argument here either tbh. 

There's no argument here other than a certain toxic community member who has past form at this kind of thing wanting to behave like a dick and picking fights in order to do so.