Arianne is an engine to develop multiplayer online games like Stendhal
Game engine supporting many 3D/2D formats and graphic effects
JavaScript framework to build game engines, games, emulators and apps
Source code of the chapters of the book 3D Game Development with LWJGL
Portable game engine with main focus on point-and-click adventures
Pear3DEngine is a modern and modular 3D development framework
Andruill Engine is a GMS (Game Management System) written in PHP.