GZDoom is a feature centric port for all Doom engine games
The Ren'Py Visual Novel Engine
05k0nz's legacy is safe
s&box is a modern game engine, built on Valve's Source 2
UZDoom is a feature centric port for all Doom engine games
Cross-platform, open source, and super fast MUD client with scripting
Games you can play in your terminal written in go
A free/open source client and automation tool for Ragnarok Online
Complete Open Source and Modular solution for MMO
Stride (formerly Xenko), a free and open-source cross-platform C# game
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
3D Game engine with editor
Skript is a Bukkit plugin which allows server admins
Cross-platform 2D and 3D game engine with modular architecture
Experimental menu for GTA 5: Enhanced
Free game engine for development of desktop, mobile, and web games
A free mixin-based injection hacked client for Minecraft
An updated version of the classic "Basic Computer Games" book
Multi Theft Auto is a game engine
A lightweight game server framework implemented with Actor Model
Voxel game-creation platform with easy modding and game creation
A completely free, open-source, 2D game engine
Cross-Platform C++ 2D/3D game engine
A free and open-source Touhou Project fangame
Kitty-Tools is a Kahoot Cheating Client for all devices and interfaces