Applies and validates a new license key to the Orchestrator. The encrypted key is decrypted to extract serial number, max appliances, and optional expiration date. For physical appliances, the key's serial number must match the server's MAC address. Virtual appliances accept any valid key and adopt its serial number. The action is logged to the system action log. License key format after decryption: SERIAL#MAX_APPLIANCES[#EXPIRATION_DATE].