When an EEPROM is signed using a license key, the serial number of the device the cape is attached to is programmed into the EEPROM. At startup, FPP checks the serial number in the EEPROM against the serial number of the device. If the two serial numbers do not match, FPP will not enable the licensed features. This is done to prevent someone from taking a signed EEPROM and copying it to multiple systems bypassing licensing. We do allow a cape to be moved to another system, but the EEPROM must be re-signed using the license key so the new device serial number can be stored in the EEPROM.