I dont know a thing about soybeans. If they self-fertilize then this guy is copying monsantos product. If any cross-fertilization from non-monsanto stock has occured than its a new product, Round-up resistant though it may be.
Soybeans self-pollinate. It's actually very difficult to get a soybean plant to be pollinated by an different plant.
I'm not sure how that makes a difference. If Monsanto can claim patent infringement, they can do so on a derivative product. The gene is their IP, not the beans.
But cross polinated beans, if such things occur, would contain DNA unique from the patented Monsanto product.