If you license your Power BI visual on Microsoft's AppSource, you won't receive a license key. Microsoft uses a system where you purchase licenses based on the number of users that will be viewing reports using the visual or creating reports using the visual. You then assign these users with a license using the Microsoft 365 admin page.
See the Microsoft Power BI Licensing FAQ.
The CloudScope visuals have field settings for license key and license validator, but these are unused in the typical AppSource environment. These fields exist only to support environments where AppSource licensing is not supported, such as Power BI Embedded or Report Server. If you wish to license CloudScope visuals for these environments, please open a support case with details about your planned environment and we'll be happy to help you out.