Nope. They're the same project. I was one of the multitudes of beta testers and I remember when they made the switch.
See the Announcements in the forum on the S3 page.
http://www.shuttlesim.be/forum/viewtopic.php?t=461
It's an awesome sim, but as I said, my computer just can't handle the new version while it runs the old demo version (S3) like a charm.