Richard.
Legal point acknowledged, But I doubt if anyone still working at the Beeb was even there when this programme was made. Even so, would they care much? This wouldn't be a worldwide release (a la Michael Jacksons last rehearsal tapes).
Just a Freebie giveaway, as an historical artifact. And I think that members of the audience on the night would be delighted to appear on a fRoots cover DVD. (Unless they were committing unspeakable clothing offences that they wouldn't want their children to see!)