Godot is a powerful cross-platform game engine
The Ren'Py Visual Novel Engine
Xash3D FWGS engine
Multi Theft Auto is a game engine
Voxel game-creation platform with easy modding and game creation
Real Time Strategy game engine supporting early Westwood classics
The game engine for everyone
A game engine powered by python and panda3d
Fast and lightweight JavaScript game engine built on WebGL and glTF
Open-source engine for Heroes of Might and Magic III
Free, cross-platform 2D game engine powered by Haxe and OpenFL
Open source voxel game engine with support for survival and crafting
Solar2D Game Engine main repository (ex Corona SDK)
Stride (formerly Xenko), a free and open-source cross-platform C# game
fheroes2 is a recreation of Heroes of Might and Magic II game engine
Powerful, mature open-source cross-platform game engine for Python
A modular Common Lisp game engine
A refreshingly simple data-driven game engine built in Rust
A retro game engine for Python
Open source clone of the Age of Empires II engine
Magic Another Game Engine
Free game engine for development of desktop, mobile, and web games
dhewm 3 main repository
The HTML5 Creation Engine
The ioquake3 community effort to continue supporting/developing id's