If I go into your garage and take your snowblower, and rent it out while you're not using it, without asking you, or giving you any money, how is that stealing?
Perhaps a better analogy is when you rent/loan out your snowblower, are you stealing from the manufacturer who otherwise could have made additional sales to your rental customers? That would cover your demand component.
So to stretch this analogy: the snowblower is the Snow Master 1.0, your own unique design, the pinnacle of years of research. Someone else comes along, magically copies it without your permission, and, having no costs to recoup, undercuts you in the market.
I don't know if that's stealing, but I do know you'll think very hard before starting work on Snow Master 2.0.