On Windows 10 a new Defender alert is open while try to install ScreenSaverGallery:

You may spread the offer of options by clicking “More info“:

The “Run anyway” option will appear. By clicking it You will be able to normally install ScreenSaverGallery on Your computer.

Note: The reasons why Windows 10 protecting you from our App is that we are using a cheaper ($499/year) version of digital certificate for signing the App (which was allowed on previous Windows versions) than the Windows 10 required Extended Validation Certificate ($699/year). According to Microsoft, it will take some time to get our App the reputation and avoid this protection.