OmniSpeak is an open source game engine for playing the MSDOS Commander Keen Galaxy Games 4, 5, and 6.
The 4th game is shareware and is free to download at the following source. https://davidgow.net/keen/4keen14.zip
The 5th and 6th games must be bought to legally utilise their .CK files
Keen 4 v1.4 EGA Keen 5 v1.4 EGA Keen 6 v1.4 EGA
Place game files in the 3ds/OmniSpeak directory.