I think it's just a little pleasure cart. Racing bikes/buggies and even jog bikes are sleeker and just don't look like this. It's what I'd expect to see tooling along behind a horse or pony on a little pleasure drive.
Pennsbury, Jerald, Houghton, Serafin, Brodeur, and a few others are all different brands that make/made similiar products, with slight variations. Which brand people use depends a large amount on where they are located as carts are expensive to ship.
The Pennsbury jog carts are popular with Saddlebred, Hackney, and Morgan barns on the east coast, as they are made in Pennsylvania. Jerald makes race bikes and jog carts as well as basket carts, fine harness buggies, viceroys and road wagons, all in horse, pony or mini sizes. Houghton, which is now out of business, made the same broad product line as Jerald.