you might not have been filled in about DRM and copy protection and all that jazz, here is some reading material for you
http://en.wikipedia.org/wiki/Digital_Rights_Management
http://en.wikipedia.org/wiki/Copy_protection
more importantly, here is the wikipedia article on audible audio:
http://en.wikipedia.org/wiki/Audible.com
In 2003, Audible made an exclusive deal with Apple to provide their catalog of books on the iTunes Music Store. Books purchased on iTunes have a .m4b extension (a variation on MP4), and contain AAC audio protected by Apple's FairPlay Digital Rights Management.
Digital Rights Management: .aa format files encapsulate sound encoded in either MP3 or the ACELP speech codec, but include copy protection by means of an Audible user name and password. Licenses are available for schools and libraries.
and your solution appears to be:
Burning/Copying: Most titles can be burnt to CD once (some leeway is allowed for bad media). Files can be copied to "authorized" devices.
so burn it to cd then rip if off.