I think the definition of monopoly should be updated to include this case. When a company sells you hardware without documenting the API or making it fully accessible, then they have a monopoly over selling software for that particular hardware.

(A similar thing would hold for business models like selling printers for cheap but making the cartridges expensive, etc.)

Meh, to me this is only reasonable if they're using some form of integrity checking to prevent you from fiddling with the bits.

To my mind, any product sold can have integrity checking, but as the owner I should be able to disable it if I want to.