I don't know about RWH PDFs from O'Reilly, but all the content in that book was made available on the author's website.
They did sort of an open editing dealy.
I was pretty sure you needed to buy the book before you get that, I tried to follow links for a while to get the RWH pdf before and didn't succeed.
Edit: Seems that they are linking only to the site and not a pdf for RWH so it could well be legal :)
Re:Free Programming Books
by OtherMichael on Tuesday May 12, 2009 @04:42PM
(#606133)
Everything I clicked on goes to legal downloads. Of course, I only clicked on a handful. But we all know there are a lot of illegal downloads out there, and I'm not seeing any that I recognize.
EDIT: I noticed that some of the random titles I looked into actually link to the book website. For example: "Real World Haskell" goes to the realworldhaskell.com website. Maybe these are legal after all? A great find indeed if they are.