I hope this isn’t too specific to be allowed.
Last month I "bought" six free cookbooks from B&N. I used Nook Study to download them but the downloaded files were PDFs. I tried importing them into Calibre (after using Alf notes to get the new B&N key and add it to the plugin), but they remained locked; I wasn't surprised because I thought I'd read that the plugins wouldn’t work on B&N PDF files.
Last night, after reading the latest posts in this thread (post 813 specifically;

bgalbrecht), I somehow muddled through the process of getting Tampermonkey and the script into Chrome and was able to download the books as epubs. This time, when I added them to Calibre, one at a time, four of the six were fine but two were still locked for some reason.
I thought I’d also read that the plugins wouldn’t work on books downloaded with Android apps (or maybe that’s just Kindle books?) but as a last resort I downloaded the two recalcitrant books into the Nook app on my Android phone (they downloaded as epubs), emailed the files to myself and saved them on my laptop. I added them to Calibre and they did get stripped. I have no idea what was different about those two books.
I don’t cook much so I may never even use the cookbooks but it gives me a great deal of satisfaction to have them under control.

Without Alf and friends I would probably have stopped buying ebooks when Fictionwise died.