Exactly this. If you think that proprietary software should exist and that companies are free to license their software under a proprietary license, why wouldn

Exactly this. If you think that proprietary software should exist and that companies are free to license their software under a proprietary license, why wouldn't a "hardware company" be allowed to do the same with their firmwares? When you buy a certain model (gopro or something else), you also buy the corresponding license. Changing the firmware to another one is probably illegal without having a proper "license" to the latter (just like you can't install Windows "Corporate Edition" on your Windows "Starter Edition" legally without paying). Of course one can disagree that this model should exist at all, but let's not pretend it's any different from proprietary software companies, there's nothing specific to hardware companies here.