A retro game engine for Python
Flexible level editor
A fancy self-hosted monitoring tool
The source code to VVVVVV
Powerful, mature open-source cross-platform game engine for Python
Simple GTK# Paint Program
A charting and data visualization library for Unity
Provides efficient allocation free async/await integration for Unity
Open source clone of the Age of Empires II engine
Mangos ZERO is a server for World of Warcraft
Enables Roblox developers to use professional software tools
You can make it - Open Source MMORPG Platform
Cross-platform, open source, and super fast MUD client with scripting
A .NET ascii/ansi console engine written in C# for MonoGame and XNA
The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
Open 3D Engine (O3DE) is an Apache 2.0-licensed multi-platform 3D
CTFs as you need them
ThinkPHP Framework
A Steam library categorizing tool
Accuracy-focused XNA4 reimplementation for open platforms
Open-source engine for Heroes of Might and Magic III
Animation Compression Library
The Tiny JavaScript Game Engine That Can!
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Vulkan renderer mod for Minecraft