Vox Populi Forum
In general I more-or-less agree with you in terms of copyright law, although I'd argue a certain amount of post-mortem copyright should be allowed. Although corporate interests have certainly abused that*.
I'll try a different way.
Project Gutenberg can't put a license and distribution agreement on a public domain work. Public domain means anyone can use said work at any time in any way, including derivatives. License and distribution agreements imply restrictions on use. Project Gutenberg (semantically) claimed ownership (copyright) on a public domain work. Conan would not like such contradictions and would say "ALL CAN READ!" ;-)
If it's public domain there's zero need to ever copy over all the additional crap Project Gutenberg added to the page, capish?
I was going to do this with Conan hypothetically learning how to use a computer, but he'd probably regard it as a "wizard box," and smash it since Conan distrusts magic.
*Side Note: We ALL know Disney bought up Pixar, LucasFilm and Marvel Comics to have "owned" characters through the rest of the century. Mickey should (as Red said) ALREADY be public domain, but I don't think Disney lawyers can extend the copyright again.