No idea. I doubt this is what you're looking for, but http://blueirissoftware.com/updates/ shows a "legacy" version. The site was redeveloped a little while back, maybe that's when the .../30/ quit working..?
Nope, /30/ quit working just a couple days ago, and includes many dozens of older versions.
I was using that page to check for Blue Iris updates without having to log in to my BI server, but I suppose the /updates/ page would serve the same purpose.