yeah that was mentioned.
Pretty sure if you sell on a device, the next person will be able to continue OB Premium.
Thought that there must be some internet authentication handshake once to unlock premium.
But actually if they do it right, all you need is some unlock code from them which is an encrypted version of your device serial number. The app will only need to compare the actual hardware serial from the USB device with the serial embedded in that code. It's easy and yeah, if done right, relatively safe.