It is made by Persei Entertainment.
On their site you will find the shareware version for download,
info on getting the registered version and a number of add-ons including my own.
Please note: The add-ons require the registered version to be played.
With the game you get Digging Jim Builder, a level editor for Digging Jim.
This is an add-on consisting of three rather complex levels.
These caves require a lot of thinking and some quick fingers here and there to get through.
The screenshots show the opening scene of each of the three caves (levels).