Following up for historic purposes and in case anyone else finds this thread, as I've been digging into the TouchTunes ecosystem.
If you look inside the control board, you'll see what looks like an empty BIOS battery holder. In a working jukebox it would hold an "
iButton" which contains the necessary information to decrypt the OS. TouchTunes uses a DS1993 iButton with 4k of storage to hold the key for decryption. While there is some readable information on the hard drive, it's not actually usable: the "real" software lives inside a protected partition that is accessed and mounted using information from the iButton (so you can't just drop an DS1993 into the slot on the control board).
An iButton works kind of like a SIM in a cell phone: it allows TouchTunes to bill the right entity for operations performed by a hardware device. However, unlike a SIM, a) the device is useless without it and b) you can't get an iButton that's not tied to anyone's account. They're more or less unobtanium: even if you found someone selling one, they would be liable for all charges you might run up unless you take over the iButton and the only way to do that is to be an operator. And the only way to be an operator is to buy 10+ jukeboxes from TouchTunes.
A vendor I spoke to put it best:
...if you have all the other parts: you have nothing. If you have an I-Button: you have a jukebox. That said this is the most important part of the entire machine and is why you don't see valid ones for sale. The I-Button IS the jukebox, not the cabinet, computer, hdd, touchscreen, ect. I-Buttons are currently going at a rate of $450 each right now and have been going up as they have stopped selling them. They have a new version now and the only way to get one is to purchase and entirely brand new $4000 jukebox. So what I-buttons are out there are all that will ever be.