I can see where the leg power concept is really a good idea, much easier on the heart. the machine is too "open source" for me, being able to slap something together with a hacksaw and drill, might mean quick prototypes, but the true functional design gets really crude.
human powered flight studies that I recall say a human can sustain 0.07 hp, so efficiency is key in this type of project.
If the main frame was built from recycled bicycle frames, joined together the weight savings would be huge.
mulch would probably be more energy efficient though, but the perseverance of the builder has to be admired.
For large gardens it is better then a push plow, but I went to raised beds & mulched to keep the water in & the weeds out.
But for corn & beans in long rows this would work after the SHTF.
If you get one, use a gas powered machine to cut new land & ready it for a year around garden, then keep it tilled & loose to grow in.
Bet it would be fun to make, a shop: welder, metal saw & a small bender & you have the tractor of your dreams.
After the gas is gone a mule or horse will be worth gold, they cost a lot to feed now.