Godot Engine – Multi-platform 2D and 3D game engine
Minetest is an open source voxel game engine with easy modding and game creation
OpenMW is an open-source open-world RPG game engine that supports playing Morrowind. Main repo and issue tracker can be found here: https://gitlab.com/OpenMW/openm...
Cross-platform 2D and 3D game engine
Open-source, cross-platform, C++ game engine for creating 2D/3D games.