Arianne is an engine to develop multiplayer online games like Stendhal
General Purpose Engine for Graphic Adventures.
Free MMORPG
Nethack 1.3d revived for other platforms
plugin-based RPG manager in C++ and Qt5
Star Trek Web browser game
The IRC's Talking Robot
Blightscape is a Private server for runescape
Free MMORPG Engine. Develop and host graphical browser-based games.