Why is it that whenever someone has something rare and doesn't instantly make it available to everyone for free, they're pilloried as greedy hoarders? It'd be a shame if this degenerates into another flame thread, so I think this should be nipped in the bud right now.
I don't think they are holding it back for reasons of profit. If I had to guess, perhaps they and their source are worried about possible legal repercussions from Lucasfilm if they release it. The copyright notice at the end is to LFL. Knowing about how they've repossessed "stolen" film prints, it's probably wiser not to take chances.
I don't think anyone is getting out the torches, we're just trying to figure out why this particular doc is being held so close to the vest.
The other four were readily available as 16mm library prints over the years, and some of these have been openly sold by collectors. Confiscating such prints is no more on Lucasfilm's "to do" list than wiping out every copy of the Holiday Special is.
Where were you in '77?