You can make it - Open Source MMORPG Platform
PyCAPGE - Python Classic Adventure Point and Click Game Engine
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Sdk library for creating 2048 game in c#.
Free strategy browsergame engine.
Gorgon Game Engine (GGE) is a C++ game engine that handles many tasks.
C++ Framework for slot machine games
Create your own online real-time browser-based MMO in your website
The next generation mud is an open-source extensible, programmable mud