Yes, a licence is required to use AirHUD.

For fully-functioning AirHUD, the user must have acquired a valid licence and entered the licence information to the controller application.

The licence information is requested on the AirHUD controller application to get started. Enter the email address that you used for registering AirHUD in the Username field, then enter the key in the License Key field.

Ensure that the user credentials (username/licence key) are correct, otherwise AirHud will not be able to validate your licence.