Yes, you can download the Windows version, and connect to your H9 from Windows. When you first connect to the H9 on Windows, it will ask you to verify that you're the registered owner of the H9. You should be able to do this without any problems using the same Eventide user name you originally used to register the H9.
If you'd like to move any presets and/or preset lists you created to Windows, if you click on the Settings button in the bottom right hand corner of H9 Control on your iPad and go to the 'Export Presets and/or Preset Lists' screen, that screen will help you export your files to an email. You can download the attached file on Windows and drag and drop it on H9 Control on Windows to import your files into H9 Control there.