So it drives the pedal shaft? Isn't that a safety hazard?
The motor sticks out uncomfortably close to the pedals and particularly on a MTB I could see a rider accidentally stepping on it...and it looks like an outrunner, so that would also be quite bad, as the foot would get launched backwards pretty violently.
This is a lot of effort compared to just bolting on a Baofang mid-drive motor. The components are also placed such that unless you have a pretty good front fender, they'll be covered in crap in no time.
There is also another detail, that you need to know, in order to understand how it all works.
Trial bikes (not trail bikes) usually have a special kind of drivetrain, where the freewheel is mounted on the crank and not the rear wheel. This allows for a very small rear wheel sprocket and extremely high gear ratios.
So to make this work, I used a trial bike crank [1] on which I'm mounting a special purpose freewheel [2]. The chainrings are mounted to the freewheel using this adapter [3].
[1] https://sickbikeparts.com/cranks-freewheel-isis-crank-set/
[2] https://sickbikeparts.com/front-freewheel-heavy-duty/
[3] https://sickbikeparts.com/freewheel-spider-4-arm-104-mm/