Gwen.Net is a port of Gwen.Net which is a .Net port of GWEN. GWEN is a lightweight GUI library aimed at games. It contains rich widget collection and most functionality you'd expect from a GUI framework.
This specific fork is adapted to the needs of the VoxelGame project.
Original GWEN can be found from https://github.com/garrynewman/GWEN and Gwen.Net from https://code.google.com/archive/p/gwen-dotnet