well, bullfrog is no more, tho its copyrights and such are held by electronic arts, and this is a area of serious gray. Id software for instance dont care much what people do with their engine code, but one need a copy of the original game to use the maps and textures. Other companies come down hard on any kind of attempt to future proof their old creations...

i guess as long as EA never considers bringing another theme hospital game out, and this fan variant never takes of in any serious way, its safe. But if they ever brought the issue to court, the judge would probably side with EA.

but i am no lawyer, just a fence-top observer of the mess that is copyright in the digital age.