Before talking about legal issues I'd like to mention the ethical one.
Google *asks* that you use the files for non-commercial purposes, and that you maintain
attribution.
Google probably can't force you to do these things, because they didn't create a new copyright
nor did you sign an agreement with them.
The MSN scanned works mostly come from Archive.org and lack such requests.
Legally, if the book is in public domain it doesn't matter who scanned it unless the scan somehow made changes. For example,
Google might own the copyright on the three pages they add at the beginning. I know how to remove those pages but most people do not.
Some people are already making commercial use of archive.org books. For example, Obscure Press is
selling the 1913
Numismatic Chronicle for $32.
http://www.amazon.ca/Numismatic-Chronicle-Journal-Royal-Society/dp/1846644380/The Product Description on Amazon was written by me! I wrote it as a mini-review of the volume when it showed up a few years ago on Archive.org!
http://www.archive.org/details/TheNumismaticChronicleAndJournalVolXIIIYou are thus probably free to make your own DVD-ROMs of the books. I started doing this, by making HTML tables of contents for some important multi-volume works like
Eckhel, but I got distracted and didn't finish it.