The only thing that the license key does is to make it possible to automatically update the plugin. Since the site won’t have access then you’d need to update manually, which would be the case with all the plugins on the site. Once you purchase Pro you will be able to log into your account to download updates, which you’ll need to do regularly since you’ll get no notification that they need to be updated. But then you should already be used to needing to check plugins and updating manually.
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