Check out what NEC wants to do with their batteries. If they have their way, it’ll be illegal to bypass their “protection” and make batteries compatible with NEC devices, allowing NEC to charge whatever they want with no fear of competitive pressure. Look for the same thing to happen with any consumable, like ink cartridges (where this stuff is already happening), toner cartridges, and even garage door openers (though there’s been some case law there already).