Hi,
Its a completely own development written in assembler.
Its proprietary / closed source. However the machine control module can be used for free without limitations. Only the CAM functions are shareware ($50) but can also be tested without limitations for some time.
One doesn’t work without the other. Unlike GRBL the Arduino will not see a single “g-code” line but heavily preprocessed instructions instead. Most of the work is done by the computer and only a few time critical tasks by the Arduino.
Christian