I love my HD+. I'm not sure if you need to register it unless you want to buy content from B&N. Even though I live outside the US, I have a US address and credit card and registered mine from overseas without problem.
If you don't want to register it, you can root or boot into the stock Android OS very easily using a preconfigured, inexpensive SD card from AFN or N2A. I use this dual boot card from AFN and it works great:
http://www.androidfornook.com/nook-s...-hdplus-detail
Also, the Kindle for Android app from Google Play works perfectly for reading Kindle books on the HD+, except that I don't like their graphic novel/comics viewer very much.