Technically, yes, you're correct. But since this is the interaction between users, owners of the service and owners of the 'proxy' service (all humans), not a JSON protocol between Python and JS scripts, there's something beyond just pure technical contract issues. If we go to the HN drinkup and I borrow a $20 from you to get a taxi home, technically I don't owe you anything, as there's no signed IOU (not even a verbal contract if I omit 'until next time'). Non technically I'm an asshole :-)