I think the Oceancontrols data sheet is a modified version of the motor manufacturers sheet, yes it does include the unipolar motors but if you check the part numbers, OC only stock the bipolar motors.
Yes bipolar motors will work if the hardware is modified, though with these high current motors a chopper(PWM) drive is preferred.
These are reasonably cheap now but need step/dir input, I can't remember if Mel's software generates step-phase or Step/Direction outputs?
True, not worth worrying about, unless you find current slew rates extremely painful
