Parallels Remote Application Server comes with two particular contracts which may be bound to a license key, i.e.:
Upgrade insurance(usually referred to as Maintenance) as well as a Support Contract
Upgrade Insurance: During the duration of the Upgrade contract, if a new major version is released, one is allowed to upgrade to it for free with the existing license key. This applies to going to new major releases. This information is applicable to the Parallels Remote Application Server. Parallels RDP Clients are provided for free.
Support Contract: allows you to contact technical support and get actual technical support should you run into issues with the product.