I wonder how much of this is hypothetical talk. Tesla has expressed an interest in opening up their charging network to partners who are willing to abide by the same terms, ie no-marginal-cost charging and up-front network registration.
I don't think it's hypothetical. You can say a lot of things about Elon Musk, particularly his propensity to meet schedules that he himself announced, but you really can't accuse him of not walking the walk when he talks the talk.
Beyond the fairness of insisting that people share the cost of the infrastructure Tesla has single-handedly created and is offering to allow use of, there are very significant risks in allowing anybody to use it. Someone could easily destroy their own equipment and try to hold Tesla liable, destroy supercharger stations, even cause fires and threaten harm or death to themselves or other people. My interpretation is simply that Tesla wants to be very sure to keep anybody away who doesn't REALLY know what they're doing, and doesn't have the skills or resources to work with Tesla to prove their implementations are extraordinarily solid. I know if it were my decision to make, that bar would be set VERY high. Being willing to share resources with other manufacturers doesn't mean they want a bunch of hackers dicking around with their industrial-power-level equipment.