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You are the boss of your Confluence spaces, and this is up to you which spaces you select to be and not be visible to the world. The app only widens search capabilities but this is done for the Confluence spaces that are visible to public already and even those you can limit in the app settings.
Will you launch a Data Center version of this app?
Yes, as of Feb 26, 2020, Data Center compatibility will be released in the next 30-60 days