"Keep circulating the tapes" is not any kind of binding legal statement.Isn't it though? You've been given permission by the copyright holder (who even if they didn't put this is the credits, at least allowed it to be in).
I love the part where the dead lady reappears on the bridge.
Riff: "Well, it's nice of them to give that dead girl her job back."
As for MST3K: The Movie (featuring "This Island Earth"), BBI was forced by the studio to edit the original film down so much (about 1/3 is missing), that the final result is not only shorter than the original film, it's also about 20 minutes shorter than an episode of the TV-show (sans commercials)! Add to that forced changes to some riffings (ex. Leona Helmsley) plus being required to drop two host segments and film a different final segment, and it's understandable why making this film was such a bad experience for BBI. (... as well as something they spoofed in a Season 7 episode: 704 - The Incredible Melting Man - http://www.mst3kinfo.com/guide/ep704.html )
Although all of this background info plus the existing deleted scenes could make for a great SE DVD one day (Criterion? )