To be honest I'm not sure to say either way. It does look homemade with the plywood back, I used to own a pipe bender I can tell you it was difficult to make both sides with the same round curve. Not easy at all I must say. Whoever made that frame knew what he was doing that's for sure. It's sold! I think for around $75.00.
For the heck of it I will try to find weird go karts and post it here.