I don't really see the issue. You are using a service called GhostWrite which uses ChatGPT under the hood. OpenAI/ChatGPT would be considered a sub-processor of GhostWrite. What am I missing?
Supposedly there is a hidden model that you can use via the API that actually is ChatGPT. One of the libraries mentioned in these comments is using it.
But that would break the server lock-in subscript model, so only downloadable software would work.