CorsixTH - an Open source clone of Theme Hospital
CorsixTH aims to re-implement the game engine of Theme Hospital, and be able to load the original game data files. This means that you will need a purchased copy of Theme Hospital, or a copy of the demo, in order to use CorsixTH. After most of the original engine has been re-implemented in open source code, the project will serve as a base from which extensions and improvements to the original game can be made.
It will run on Windows, Mac and Linux.