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
The engine now supports ImGui!
This is not a VGUI2 replacement, it's meant for internal use only by engine developers. VGUI2 will be based on another library and will be exposed to new client dlls/gameui. ImGui will be used as an internal GUI library implementation without requiring VGUI1/VGUI2