If you do not have a key, you simply click "Close" or "Later." The software continues to work 100% perfectly.
The registration key enables users to utilize advanced features that are not available in the free version. These features are designed to improve productivity and efficiency in file management. Cyberduck Registration Key
David V. Kocher, the lead developer, has publicly stated multiple times on the Cyberduck mailing list and GitHub issues: If you do not have a key, you simply click "Close" or "Later
Users can acquire a registration key through two main channels: the lead developer
After donating, a registration key file will be sent to your registered email address.
Double-click the .cyberducklicense file sent via email. The OS will automatically pass this to the application.