I can't speak for how pg feels, but that is a very different kettle of fish.
In your case, you'd have been modifying and distributing his content, rather than providing users a tool for consuming content they have obtained directly from pg.
Think hosting mirrored ad free sites vs creating AdBlock.
He might still have a problem with this (if only because of server load), and it would have been a good idea to check first, but your experience isn't evidence one way or another.
Impressive how short this can be with the right libraries: 40 lines of code to scrape an index, download the pages, get the right parts, and make them an ebook.
However, wouldn't it be more efficient if one person would do this, and publish it? Now everybody has to scrape PG's site. Thanks for the code tho!
I tried running it and it chokes on "Chapter 1 of ANSI Common Lisp". I think that's due to the link being a txt file rather than html, causing an exception to be thrown: "Error: URL doesn't exist".
Those essays are available for free on his site. If you want to scrap it for yourself, you're in a grey zone, but it will be fine. But hey, authors deserve respect : if an author wants to publish an ebook, he will.
edit: just checked my email, i actually asked him about putting up the epub, not the script. but same difference I suppose.