Azuriom is a complete open-source web solution for game servers
A lightweight game server framework implemented with Actor Model
Distributed server for social and realtime games and apps
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 mobile game distributed server implemented using netty4.X
The best code this side of the galaxy