http://archive.konte...om/junkman.html
Looks like it was a clone by a garage coder. Like a lot of TI and CoCo stuff. But if you can find the files and a good emulator, give it a try. There are a great number of hidden gems out there in clones of popular games. I find the differences in implementation fascinating, and the added twists or features the cloners often introduce can be a lot of fun.
This is true of some commercial games as well. The Jak & Daxter series were great but only available on Sony platforms. Mainly the PS2, with an HD remake collection now coming to the PS3. If you wanted more of that gameplay or didn't have a PS2, the great alternative was the Ty the Tasmanian Tiger series from EA. These were on the Nintendo GameCube, the Xbox, and the PS2 and were priced at bargain levels. They can still be played on all but the most recent Wii models and on the Xbox 360 under emulation.