Open-source engine for Heroes of Might and Magic III
KorGE Game Engine. Multiplatform Kotlin Game Engine & Korlibs
A completely free, open-source, 2D game engine
Solar2D Game Engine main repository (ex Corona SDK)
Game engine supporting many 3D/2D formats and graphic effects
Embeddable unity game engine view for Flutter
A cross-platform, open-source, pure C game engine for mobile game
Urho3D Game engine
Blueshift is a cross-platform 3D game engine implemented in C++