Phil,
Early versions of Dos-2-Dos would only read IBM disks. If a disk were
formatted on an IBM (3.5") and then used on an ST, then Dos-2-Dos could read
it. Current version of Dos-2-Dos does directly read and write ST disks. I'm
not sure of the vendor's upgrade policy, though – for that you'll have to
contact Central Coast.
Hope this helps…Bob