The motofail2go_windows.zip also includes a "run.sh," which works in MacOS. I expect it would work in GNU/Linux, too. The su and Superuser.apk mentioned here and in the original thread are still needed, though.
Try a DK17 ROM. It works there and was broken in DK28. As far as I know, noone knows why. You can use the DK28 modem with a DK17 ROM.