As Chosker says, the license is only needed to edit. Any created content will always be usable.
The one off fee (which I think is £100) is just that; it’s a one off fee including all updates. However is only for small indie teams (<5 employees and a budget <£400,000). Teams not fitting those requirements will need to purchase licenses using the normal pricing structure.
And the tool doesn’t need to always be connected; it only needs to authenticate once. I’m not sure whether you’ve assumed it was online-only or you’ve had troubles with the plugin offline; if it’s the latter do let me know and I can look into it for you.