The HTML5 Creation Engine
The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
3D Game engine with editor
2D JavaScript Physics Engine
Ct.js is a desktop game engine that makes learning programming fun
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Kotlin extensions for the libGDX game framework
Open source library for creative expression on the web, desktop, etc.
A .NET ascii/ansi console engine written in C# for MonoGame and XNA
KorGE Game Engine. Multiplatform Kotlin Game Engine & Korlibs
Python MUD/MUX/MUSH/MU* development system
Go bindings for raylib, a simple and easy-to-use library
A modern, cross-platform Quake game engine based on FitzQuake.
GemRB is a portable open-source implementation of the Infinity Engine
Royal Entertainment Graphics eXecution (REX)
Orx: Portable Game Engine
Old-school 2D game engine
A cell-based puzzle game featuring classic and completely new puzzles
Amateur 3D Game Engine
Vivid3D is a C++ IDE/3D engine, with python scripting.
SDL based generic 2D game engine
Game engine supporting many 3D/2D formats and graphic effects
API (C#) for simulating certain aspects of a ZX spectrum for porting.
PyCAPGE - Python Classic Adventure Point and Click Game Engine