3D C++ Game Engine - yet another open source game engine
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Amazon Lumberyard is a free AAA game engine
QQ Group:538722494,KSFramework = KEngine + SLua(or xLua)
mGSTEP port of the Cube game engine
Improved version of the X-Ray Engine, the game engine
2D Game Engine with Lua Scripting made on top of SFML
A cross platform Lua based game engine
Data-oriented and data-driven game engine written in Rust
KlayGE is a cross-platform open source game engine
Cross-platform 2D and 3D game engine
A cross-platform 2D game engine
Clojure in Unity
Opensource Game Studio
A fast, scalable, distributed game server engine/framework for C++
Planimeter Game Engine 2D - LÖVE-based game engine for Lua
Low-Level Game Engine for Retro Platforms
Real-time RPG for PC/tablet/phone; multiple quests and random dungeons
Blueshift is a cross-platform 3D game engine implemented in C++
Web powered cross-platform 3D, WebXR game engine
Portable game engine with main focus on point-and-click adventures
OpenSAGE is a free, open source re-implementation of SAGE