This is the response to my questions to the folks at HTC:
"We certainly understand wanting to make sure you can keep your HTC One up to date despite the unlocked bootloader and can provide some information to help answer your questions.
Unlocking the bootloader on any HTC device actually prevents the phone from receiving official updates. This is because OTA updates are signed and phones with unlocked bootloaders will not be able to verify the signature."
"In regards to your concern about the 64GB unlocked version, the bootloader cannot be reverted to a locked state; nonetheless, you should have no trouble whatsoever with DRM if you do not use the device for not legal purposes.
Please reply to this email if you have further questions or concerns." --- I doubt this last statement...
"We certainly understand wanting to make sure you can keep your HTC One up to date despite the unlocked bootloader and can provide some information to help answer your questions.
Unlocking the bootloader on any HTC device actually prevents the phone from receiving official updates. This is because OTA updates are signed and phones with unlocked bootloaders will not be able to verify the signature."
"In regards to your concern about the 64GB unlocked version, the bootloader cannot be reverted to a locked state; nonetheless, you should have no trouble whatsoever with DRM if you do not use the device for not legal purposes.
Please reply to this email if you have further questions or concerns." --- I doubt this last statement...