No one said a Nook was an Android-based product. However, if you owned a Fire and you wanted some apps, why would only Android apps run on it?
The Nook is exactly the same case as the Kindle Fire, both of them are based on Android and can run Android programs but none of them are Android products.
Someone in this thread mentioned that it's not so hard to write for the fragmented Android market because you just write for the lowest common denominator - like one size fits all. That's gotta really suck, unless you're running the oldest OS version with the smallest screen out there.
And that claim is totally wrong, you only write apps for the lowest common denominator if you are a bad developer.