Kindle Users Forum Official News
Apple no longer require an ISBN to publish on iBookstore
In the past, publishing on Apple's iBookstore has required the publisher to purchase an ISBN (International Standard Book Number), something which could add a significant cost. This requirement made Apple's platform less appealing to indie authors than similar offerings such as KDP and sites like Smashwords, who provide multi-channel publishing, were the only real way to avoid the necessity for an ISBN,
In recent changes to their publishing guidelines however, Apple have now made an ISBN a desirable option rather than a mandatory option, so direct publishing on the iBookstore is now viable for anyone publishing on a shoestring.
You can read about the changes in the FAQ here : http://www.apple.com...