Stride (formerly Xenko), a free and open-source cross-platform C# game
You can make it - Open Source MMORPG Platform
Ct.js is a desktop game engine that makes learning programming fun
Gideros Release version
16 bit real mod minecraft clone running in bios
realistic driving simulation + functions for 2D/3D graphics
Enigma is a puzzle game
Game framework with AI
Prince of Persia reimplementation written in HTML5 / JavaScript
Haskell game engine library for roguelike dungeon crawlers
Rust library to create a Good Game Easily
MIT Licensed Open Source version of Torque3D from GarageGames
Real-time collision detection and multi-physics simulation for VR
A free car race simulator game for casual gamers, based on TORCS.
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Vivid is a modern C++ 3D engine using OpenGL4+
OpenGL port of the classic 6dof 3D shooter Descent
Amazon Lumberyard is a free AAA game engine
3D C++ Game Engine - yet another open source game engine