MicroPrint is a command-line program for Mac. It takes a G-code file that you've previously sliced in a slicer like Cura, pre-processes the code the same way M3D does it with bed level measurements, ...
I tried opening the "uHoubolt.step" in various programs. I reported the issue on the FreeCAD forum, they say it's likely an issue with the file: https://forum.freecad ...