It might be fun. Especially if you had two, and raced 'em. Or bolted on a trailer hitch so you could pull a wagon.
One observation: There's no mention or sign of multiple speeds, and it is sure to be geared pretty low. That might get tiresome after a while, unless you figured out a fix to make it a little more versatile.
So, what do you think? If I got it, I'd just use it for tooling around the farm, maybe run down the road to the grocery store every so often.
It would be fantastic! BUT....
The pedalling position is very inefficient, it would greatly be improved by the guys seat being raised a good 50cm. Then his legs would be fully outstretched on the bottom of the stroke (and maybe get some longer cranks, cause those look like kids cranks.)
But as mentioned if those problems were resolved, a fantastic farm and offroad bike this would be.