Desktop/Android/HTML5/iOS Java game development framework
One framework for creating powerful cross-platform games
DeSmuME is a Nintendo DS emulator
Cross-Platform C++ 2D/3D game engine
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Free and open source real-time strategy game
Open 3D Engine (O3DE) is an Apache 2.0-licensed multi-platform 3D
Powerful, mature open-source cross-platform game engine for Python
A charting and data visualization library for Unity
3D Procedural Game Engine Using OpenGL
Doom-based AI research platform for reinforcement learning
3D game engine/framework in C, with Luajit and Python bindings now
Flax Engine, multi-platform 3D game engine
Gideros Release version
The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
Parabator 2 - Free 3d board game
A work-in-progress PlayStation 4 emulator
FlightGear Flight Simulator: free open-source multiplatform flight sim
A modern, cross-platform Quake game engine based on FitzQuake.
3D Engine c++
Odamex is a free, cross-platform, modern client-server Doom engine