Interesting new, I just checked nessus.org and registered myself for the second option of plugins. Just want to clear that Nessus alone still an open source project, that seems to keep “community/gpl” plugins for free but will send up-to-date plugins only to people paying.
I guess they have the right reasons, and as the article says, a good balance that permits to keep part of the project as OSS/GPL. Perhaps in the future this will become something like Redhat/fedora or openOffice/staroffice kind of thing.
Thanks for the news.