Flax Engine, multi-platform 3D game engine
Cross-platform 2D and 3D game engine with modular architecture
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
The Ren'Py Visual Novel Engine
Cocos simplifies game creation and distribution with Cocos Creator
s&box is a modern game engine, built on Valve's Source 2
Cross-Platform C++ 2D/3D game engine
3D engine with modern graphics
GZDoom is a feature centric port for all Doom engine games
An OpenGL RTS game engine written in C
Simple and light-weight 3D game engine
Multi-platform 2D and 3D game engine
UZDoom is a feature centric port for all Doom engine games
An unofficial rules engine for the world's greatest card game
3D Game engine with editor
Stride (formerly Xenko), a free and open-source cross-platform C# game
A completely free, open-source, 2D game engine
Multi Theft Auto is a game engine
Powerful, mature open-source cross-platform game engine for Python
Free game engine for development of desktop, mobile, and web games
The most powerful PowerShell module for fine-tuning Windows
3D Engine with Blender Integration
Complete Open Source and Modular solution for MMO
Cross-platform, open source, and super fast MUD client with scripting
A modular Common Lisp game engine