I’m not sure if he will provide an unlimited free license of Dante just because the lack of mega menu in Neighborhood, especially as it’s in the making.
Yes you have the files for Dante, but not sure why you need the license key? You do not need it to update the theme, as the updates are pushed to WordPress.
I’m afraid it’s Envato that provide the licence key, not the theme owners. Don’t worry, Ed is aware that he has provided you with the files, and it is very unlikely that anyone else will ask for your licence key.