> Not only must they not mind, but they must actually support the new forum - put links to it on the firebird websites eg. ibphoenix.com and firebirdsql.org and firebirdfaqs etc.

That's not a problem. If you look closer, you'll find there links to
different firebird-related forums in different languages. Your one will
be just another.

> Also, who would be the rightful administrators of such a forum?

If you create it - you'll be the administrator and fully responsible
person.

> What Forum sections will we have? Just a general help section? Or would we divide it up into "Installation" "Security" etc.

And as forum's administrator and owner you'll decide all these question.

SY, SD.