What the article said was:
No reason is offered by the bookseller but it is telling that even though it already has the app on the BlackBerry, and it allows purchasing content from B&N, it is no longer going to let that happen. Perhaps the company finds it too expensive to maintain and support the BlackBerry. It is a drastic measure to kill a platform that can currently purchase content.
Blackberry is shifting from its current BB OS to QNX (aka Playbook) OS for all upcoming phones. It has already stated no new phones will be released with BB OS. That means B&N would have to re-engineer the Nook app for the new OS and decided it didn't have the development money to do so. B&N is very, very strapped for cash and is eyeing every savings it can while it builds marketshare for Nook.
And, the Playbook QNX OS is about to be refreshed with 2.0 (third week Oct) which will include an Android apps layer. B&N will still be able to support Blackberry using that.