CorsixTH is a free open source clone of the Theme Hospital game. Works on Linux, Windows and Mac and looks like oodles of fun. You’ll need the original game files to play.
CorsixTH, an open source clone of the classic game Theme Hospital, has released Playable Beta 1, making it the first open source Theme Hospital clone to reach playable status. Representing five months of development since the project launched, CorsixTH Playable Beta 1 implements many of the features of the original game, and runs natively on Windows, Linux, and OS X. This intent of this release is to increase awareness of CorsixTH, and to encourage more developers to assist in the project.