Not sure about the Snapscan Touch, but have you checked out XSane (which I had used in Linux with my Acer/Benq Scanner (part of the Snapscan group) and was then able to setup in OSX using "Twain-Sane for Mac OSX".
Check out the following:
This takes a bit of setting up and requires the same firmware file .bin as that supplied in the windows driver disk. You'll need to edit a file using Emacs. Check out Xsane (a Linux programme) for details.
Rosetta is designed to enable all Power PC Mac OSX programmes work with the new Intel chip, so in theory your existing scanner programme should also work.