Gutenberg.org is just so unreadable. It’s a damn shame that the classics of the ages are hidden on a website no one would choose to read on. Why is there no Penguin Books for the web?
That licence only applies if you want to use the term “Project Gutenberg,” which is trademarked. As noted at the top of that page, the actual book text isn’t protected by copyright at all, and you can do anything you want with it,.
They don't have Symbolic Logic, though.