"Borrowing" a book just means you can view it on the clunky web reader for one hour? Other online librarians (for the lack of a better word) like Proquest lend books using the Adobe Digital Editions platform, I think that would have been a better approach.
Edit: So it appears OpenLibrary does lend through ADE, but this feature is not applicable for all borrowable books. Some can only be borrowed for one hour, at least in this redesign.