OGS Engine is a GoldSrc game engine reimplementation using only original id Tech 2 (Quake/Quake 2) engine (and its forks) sources with some bits from the id Tech 3 engine and no reverse-engineered code
c1a1 (HLA)
Actually, per-texture palette for map textures is already supported, just haven't tested it out before
There are some issues with lighting, though, because GS uses 3 bytes for lighting data and OGS' gl render code still contains some pieces where it operates on 1 (as original Quake does)
After fixing the QW prediction code, player's roll angle is set to 80 for some reason. This happens in QW too, but it has a hack that fixes that (and, after looking at HL's view code and comparing it with QW's I dunno if we need cl.simangles field at all (it might be used by the demo playback code, can't say for sure))
Still cannot move, because pmove code thinks I'm dead (and spectator movement speed is set to 0(?)) and game dll still can't properly spawn players, but I'm close to fixing that up