Godot is a powerful cross-platform game engine
Multi Theft Auto is a game engine
fheroes2 is a recreation of Heroes of Might and Magic II game engine
Open-source engine for Heroes of Might and Magic III
Real Time Strategy game engine supporting early Westwood classics
Xash3D FWGS engine
The Ren'Py Visual Novel Engine
Voxel game-creation platform with easy modding and game creation
Open source clone of the Age of Empires II engine
Descent 3 by Outrage Entertainment
Cocos simplifies game creation and distribution with Cocos Creator
dhewm 3 main repository
The game engine for everyone
The ioquake3 community effort to continue supporting/developing id's
3D Procedural Game Engine Using OpenGL
Open source voxel game engine with support for survival and crafting
A game engine powered by python and panda3d
Recreation of the classic Grand Theft Auto III game executable
An OpenGL RTS game engine written in C
3D Game engine with editor
RPG Maker 2000/2003 and EasyRPG games interpreter
Fast and lightweight JavaScript game engine built on WebGL and glTF
A complete 3-D game development suite written in Java
Solar2D Game Engine main repository (ex Corona SDK)
LayaAir is an open-source 2D/3D engine