The source code to VVVVVV
Open source HTML5 game framework that offers WebGL and Canvas
Open-source Android/Desktop remake of Civ V
Desktop/Android/HTML5/iOS Java game development framework
A simple and easy-to-use library to enjoy videogames programming
Open source library for creative expression on the web, desktop, etc.
Open source cross-platform multi-purpose game toolkit
Free, cross-platform 2D game engine powered by Haxe and OpenFL
Action-adventure game originally released in 2013
Open source library for N64 development
A completely free, open-source, 2D game engine
Android, UIQ 3.0, Series 60 Edition 5 open-source software
Gideros Release version
Use the Delta Executor APK with Roblox on a Windows PC.
Portable version of the incredible Godot Game Engine
Examples of procedural geometry for Unity3D C#
Source of Mana is a unique 2D MMORPG
A multi-purpose file manager for the Nintendo Switch
Flex roguelike
Map creator for the BattlleTech MUX
Flash Quiz TV (A quiz game for all family)
Asphyre is a cross-platform framework for Delphi and FreePascal.
The Atomic Game Engine is a multi-platform 2D and 3D engine
Open-source, cross-platform, C++ game engine for creating 2D/3D games
Modern AS3 Game Engine