Voxel game-creation platform with easy modding and game creation
Open-source engine for Heroes of Might and Magic III
Solar2D Game Engine main repository (ex Corona SDK)
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Cross-platform game engine in Rust
A completely free, open-source, 2D game engine
GemRB is a portable open-source implementation of the Infinity Engine
Urho3D Game engine
A cross-platform 2D game engine
Blueshift is a cross-platform 3D game engine implemented in C++
Open-source, cross-platform, C++ game engine for creating 2D/3D games
Cross-platform 2D game engine