Arianne is an engine to develop multiplayer online games like Stendhal
LGSL (Live Game for PHP 5.4-8+: online status for various gameservers
A fun realistic multiplayer free-and-open-source first-person-shooter!
Cross platform administration tool for Source Engine dedicated servers
Yet Another PHP EVE API Library.
Rigs of Rods Multiplayer server
Automatic chooser of optimal fleet (with limits) for ogame browser gam
Game framework on top of Python, Panda3D and Twisted