Pie in the Sky Software was founded in 1987, but became better known in 1992 when their shareware flight simulator Corncob 3D was released. Later they developed the Pie in the Sky 3D Game Creation System, which allowed users to make their own Wolfenstein 3D-like games. It was used to make some of Pie in the Sky's own games like Lethal Tender, as well as user-made games.
Official Pie in the Sky Software website
Pie in the Sky Software's Mobygames page
Pie in the Sky Software's Wikipedia page