RTSish Game Engine
Commander Keen Interpreter
2D Game Engine
Improved version of the X-Ray Engine, the game engine
A fast-paced free software rally racing game
mGSTEP port of the Cube game engine
3D Game engine with editor
A distributed graph deep learning framework.
KlayGE is a cross-platform open source game engine
A fun realistic multiplayer free-and-open-source first-person-shooter!
A 2D game engine and level editor
A cross-platform 2D game engine
IGS Labs
A cross platform Lua based game engine
higan is a multi-system emulator focused on accuracy & preservation
A fast, scalable, distributed game server engine/framework for C++
Cross-platform 2D and 3D game engine
Vivid Engine 2 is an open source 3D Engine coded using C# and C++.
Opensource Game Studio
Character animation system for games and simulations.
Free and Open Game Programming Language for Windows and GNU/Linux