Apple eyes authors with new iBooks Author app

Sooo ... how locked into Apple's ecosystem are books created in this way? The notes say:

• Submit your book to the iBookstore for sale or free download with a few simple steps* • Export your book in iBooks format to share on iTunes U or to give to others • Create a version of your book as a PDF file

That footnote is: "Books may only be sold through the iBookstore; additional terms and conditions apply."

So if you export the PDF, can you submit that PDF to, say, Amazon's print on demand service?