Hmmm, I'm not sure. Let's see, I purchased v 5.15 on 5/2001, updated to 5.5 sometime after that (these were the workgroup products), then updated/lateraled to 7.5 (Professional) on 10-2006 for about $45, 7.7 on 12/2009 for about $32.
They periodically provide free maintenance updates to resolve problems or add support for new backup hardware (tape drives, etc).
The product has gone though a couple of owners, originally Dantz, then EMC, then Roxio (blah), and finally went back to being independent within the past last year. I believe some of the original people are still with the team. EMC, and especially Roxio, were lost as to how to market the product, and their purchases seemed to make little sense (EMC had a competing backup solution, Roxio was the wrong vendor for a professional-grade product).
The Windows version of late seems to be playing second fiddle to the Mac version. It is still solid, but took EMC forever to come out with 7.7 for Win 7. (I can't help but think of the SlimDevices products, after being purchased by the inept Logitech.)
There were very few solutions for workgroups / servers; and this product is still a fine choice.