This link is no longer valid. You can find the Unitrends virtual appliance here: http://www.unitrends.com/products/software/download
Note three Editions are currently available:
Free Edition -- 4VMs, Free Forever. Online support available.
30-Day Trial Edition -- 30 days, no limits on ANYTHING; phone support included. You can revert to Free Edition after 30 days.
Enterprise Edition -- per TB and per resource licensing options available to best support your environment (and budget)