> One person or legal entity may maintain no more than one free Account

This means that for nearly all of us it is one account per person.

The rules are more relaxed for corporations

https://docs.github.com/en/site-policy/github-terms/github-c...

> A User’s login may not be shared by multiple people.

and that's it.

So there could be joe@company1.com, joe@company2.com, etc. Probably only the joe in his current company can login because the others have revoked its access.