The first time you start Vaadin Designer, it will ask for a license key. You can obtain a free trial-license or use the license included with your Pro Tools subscription. For instructions on how to install the license, see "Installing Commercial Vaadin Add-on License".
Please note that a separate license key is required for each developer. If you choose not to enter a license, you will be unable to save your design.
If you for any reason need to remove or change a valid license, it is located in ~/.vaadin.designer.developer.license in UNIX systems and C:\Users\<username>\.vaadin.designer.developer.license in Windows.