Yeah, but the Making Of didn't have Jefferson Starship playing a song in the middle of it. They probably got the rights to broadcast it, but never got the rights for other types of distribution - that's why so many TV-DVD releases today have the music replaced with generic, royalty-free music, and why many haven't been released at all. Look at any DVD release of That '70s Show, season 1 of Scrubs, and older shows like Mission: Impossible or WKRP in Cincinnati. They even had to replace the theme song for one season of Married ... with Children, for Christ's sake.

So when you have something that's played live during the program, the studio might very well think it's not worth it to pay the royalties for home video distribution (which, for Jefferson Starship, would probably be fairly high) if they don't think they'll make their money back.

Of course, I don't think that's why the Holiday Special hasn't been released - I just think George hates it and never wants it to see the light of day. Once he's dead, and he isn't personally responsible for these decisions, we'll probably get awesome Blu-Ray releases of the 1977, 1980, 1981, 1983, and 1997 versions of all the films, and a very nice DVD of the Holiday Special. But that might be a while ...