It depends on which AirServer product you use.

AirServer Connect (hardware)

No license is required. Once you purchase the device, all features are included with the device, including AirServer Cloud Management.

AirServer software editions

Yes, a license is required to use AirServer for Mac, Windows, Xbox, or Surface Hub. You can download AirServer and try it for free during a trial period, but a valid license is needed for continued use.

See the Licensing & Activation for details on how to purchase, activate, and manage licenses.