That does seem out of date. The post is more than 2 years old, and even it apologizes for having been out of touch for a while.
BackupPC, which does file level de-duplication, is being supported by Zmanda now --
http://www.zmanda.com/backuppc.html. It is open source and has been around for a while.
I doubt you'll find something quite like Falconstor, but, you shouldn't have any trouble putting together a high quality backup and archiving system with open source software. You just have to think in terms of setting up a working system, rather than specifically trying to replicate how some other product works.
You could use a couple of products together to achieve the end results that you want.