CTFs as you need them
One of the best Prodigy hacks
Mangos ZERO is a server for World of Warcraft
Empowering everyone to host fast and efficient Minecraft servers
PufferPanel is an open source game server management panel
MCDaemon, a python tool to control your Minecraft server
Archipelago Multi-Game Randomizer and Server
Free, Secure, Distributed, Modern Control Panel for Minecraft
Fully async, multithreaded, predictive, open source, 3.01 reach
Minecraft map editor and mod
The Tiny JavaScript Game Engine That Can!
Experimental PlayStation Vita emulator
C# application with primary purpose of farming Steam cards
Open source clone of the Age of Empires II engine
A free/open source client and automation tool for Ragnarok Online
Magic Another Game Engine
LSJ-Server-Terra (Java Multipurpose Sever connected with MariaDB)
A fancy self-hosted monitoring tool
A permissions plugin for Minecraft servers
You can make it - Open Source MMORPG Platform
Open source Old School RuneScape client
Python MUD/MUX/MUSH/MU* development system
Classic America's Army