The Zombie engine is an open source game engine and framework based in The Nebula Device 2, the open source engine from Radon Labs. Developed by Tragnarion Studios, it is mainly oriented towards the creation of multiplayer PC action games.
Zen Worlds is an object oriented C++ virtual worlds / MMO game engine framework. This project includes Zen Engine game engine client, Zen Enterprise, an Enterprise Service Bus, and a C++ Application Server, and Zen Studio, a game development IDE.