The activation algorithm for Windows XP has, incredibly, finally been completely cracked, allowing for totally offline activation, according to The Register (via Ars Technica). A blog post on tinyapps covered a Reddit post discussing it, but the program allowing it has apparently existed for at least several months, possibly floating in the ether as a torrent download.
As for who created the software, nobody in the subreddit post knows, including user retroreviewyt, who first shared it and isn’t even sure where they got it from, speculating it came from from a torrent somewhere.
In the meantime, someone appears to be working on reverse engineering the software. A user calling themselves Neo-Desktop dropped the program into Github and said in a discussion there that they are working to create an open source version.