"The digital books in Barnes & Noble’s e-bookstore are available in either epub or Adobe Pdf format. Customers who want to buy books in those formats from other digital bookstores may do so and transfer them onto the Nook, but those who want to buy e-books directly from the device will be connected to Barnes & Noble’s own bookstore."
I can always find a way to get a Nook overseas but I will most likely miss out on discounted ebooks offered from B&N. Looking at bestsellers Lost Symbol sells for about $10 on Amazon and B&N (Kindle Intl +$2), but the site you mentioned, BooksOnBoard is selling it for nearly $25. Seems like if you want affordable ebooks Amazon and B&N are the safest bets (an observation, I'm not an expert.)
Assuming you can transfer B&N books via the USB cable has anyone successfully bought B&N ebooks from overseas using a US credit card? Do they have a proxy block as well?
The only related comment I found was this "Barnes & Noble has said that it is looking at an international roll out however failed to mention a time frame when Pocket-lint asked."
Pocket-lint being the name of this site: http://www.pocket-lint.com/news/2808...ble-nook-ebook