I purchased a Book Courier three months ago and a Book Port only about three
weeks ago. Book Courier's User's Guide explicitly states that up to three
Couriers can be activated for Audible.com, the inference being, of course,
that this might be in addition to the three other allowable devices. I'd
definitely activated my quota of items, so my subsequent attempt to also
activate my Book Courier was strictly anecdotal. It worked, however, and
the activation succeeded without my even having to go online. Not a typical
Audible.com practice.
Book Port's manual states that only three devices can be activated at a
time, and no attempt was made to indicate the possibility that Book Port
might be exceptional in any way regarding this policy. Again, though, my
activation went through without a hitch. By all means turn your computer's
volume down at this point and forget this message as soon as you read
it--but--but, it seems to me as if our units are being granted special
status. For one thing, all other devices must receive transfers through
Audible Manager. If you've reached your quota of Ipods and other
traditionally marketed units and you've not tried activating your Book
Courier, give it a try. It worked for me, and I'm certain it will for you.