CTFs as you need them
MCDaemon, a python tool to control your Minecraft server
Open source clone of the Age of Empires II engine
Archipelago Multi-Game Randomizer and Server
A free/open source client and automation tool for Ragnarok Online
Python MUD/MUX/MUSH/MU* development system
Arianne is an engine to develop multiplayer online games like Stendhal
GameServer is a sophisticated, game server designed for online games
Get easy bot lobbies in any game with our bot lobbies tool.
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Private Online Game Launcher for Any kind of Game
The Pokemon Go Bot, baking with community
A maintenance toolbox for cleaning up Space Engineers saves.
Server software written in Python that implements the MUCK protocol.
Open Source Virtual World and MMOG Development Platform
A Python Based YSFlight Server Extension