Today marks the release of the FDS 6 beta, (release candidate 1). More details are give in the official release announcement. A large number of changes and improvements have been made in the last couple of years, which are summarized on the FDS release notes and Smokeview release notes pages.
You can read about the FDS 6 beta testing details at the bottom of the FDS website.
As mentioned in my post on the FDS-SMV development blog, be sure to take advantage of all of the FDS-SMV collaborator resources during the beta test process (and beyond).
Happy beta testing, and we look forward to hearing comments and feedback from users via the FDS Discussion Group and Issue Tracker!