You are just a glitch in their system. They won't check the content of private repos, and they probably also do not check if there is free software hosted at the same account, so you might have found the hole in their good will.

But their limit seems around 100 MB storage-usage, so I guess it's within their abilities to tolerate some glitches.

Ah ok, well, save for some drafts I wouldn't mind opening the repo which is just a Hugo system intended for a public website anyway. But good to know. Perhaps I will self-host that forgejo instance then :)