The maintenance contract (contract) usually contains a clause that allows the licensee to receive minor updates (V.1.1 = > 1.2) and sometimes larger updates (V.1.2 = > 2.0). This option is usually referred to as upgrade assurance or upgrade assurance. For a major update, the customer must purchase an upgrade if it is not included in the maintenance contract. For a maintenance extension, some manufacturers charge a retroactive reinstallation fee per month if the current maintenance has expired. Since many proprietary „licenses“ list only the rights that the user already has under 17 U.S.C. § 117, and yet advertise that they take rights from the user, these agreements cannot be taken into account. Proprietary software licenses often claim to give software manufacturers more control over how their software is used by retaining ownership of each copy of the software from the software manufacturer. .