More on Book Search PDF Downloads

After a bit more research, there are some interesting things about Book Search's new PDF download option for public domain books. Google Blogoscoped noticed that when you download one of the PDFs, the file itself contains an introductory page that attempts to restrict the usage of the public domain book at issue. Interestingly enough, the Google Book Search Help Center does not mention any such restrictions. Also, Book Search, both on the intro page in the PDF file and the Help Center page, requests that users not remove Google's watermark from the PDF. This is peculiar because one can republish a public domain work and copyright that version, yet Google is copying someone else's version and pasting their logo on it, asserting that they have some proprietary interest over it.

So questions remain. Can Google legitimately restrict access to public domain works? And is it proper for Google to brand these copies and require that others not mess with it?