How old is that letter?
I remember reading a year or so ago that OpenAI used to have a charitable charter, but after their boss provoked being ousted to then have shareholders insist he be brought back in and then cleaned house, I remember hearing that these rules in the charter would get removed.
I'm presuming they're of the impression that these clauses are still valid, or the removal took its way to wind through some bureaucracy and they're now trying to stop it one last time.