- Apos.Gui (C#, MIT, beta)
- Box2D (C, C++, Objective-C, zlib, mature)
- curses (C, ?, mature, inactive since 2000)
- Dear ImGui (C, C++, MIT, mature)
- DirectPython (C++, 2-clause BSD, beta, inactive since 2007)
- FreeType (C, GPL-2.0, Custom, mature)
- GBDK (C, Assembly, C++, MIT, mature)
- GeonBit.UI (C#, MIT, mature)
- Horde3D (C++, EPL-2.0, mature)
- ncurses (C, MIT, mature)
- Penumbra (C#, MIT, mature)
- PGU (Python, LGPL-2.1, mature)
- pyscroll (Python, LGPL-3.0, mature, inactive since 2018)
- PyTMX (Python, LGPL-3.0, mature)
- Simple and Fast Multimedia Library (C++, zlib, mature)
- Simple DirectMedia Layer (C, zlib, mature)