CloneKeen is a GNU GPL-licensed imitation of the original game engine used for the Keen: Vorticons trilogy, written by Caitlin Shaw. It is designed to be portable to all compatible UNIX-style operating systems, and the Win32 (Windows) platform, by relying on the SDL library for multimedia. Alternate engine ports are maintained by other authors. The last release dates from November 19th, 2005.
Only the engine is included in the clone. For actually running the game you need to get the original Keen 1 shareware version, and/or purchase the other episodes of the Keen: Vorticons trilogy from Apogee (publisher) or Id Software (developer).