Just to avoid that people are getting confused when following this thread:
The above conclusion is WRONG. You CAN run the 28BYJ-48 with the EasyDriver. It's indeed just a matter of connecting only the two coils (pink & orange and yellow & blue) as A & B on the EasyDriver board, leaving the common (red) untouched. For just a quick testing (without load on the motor) you can get the 5V for the EasyDriver from the arduino board (wired on a breadboard e.g.).
Another source of confusion for me, was the 'step size' parameter. Note that according to the ASCOM description, this gives the movement of the focuser per step of the motor (in microns). In the focuser apps I saw this parameter used to define how many steps the focuser motor rotates per button push (when in relative mode). So, obviously, when you set the step size to e.g. 0.35 microns (which is about what I calculated for my setup with all the gearing (in the motor + the belt and pulley drive, I use), you will never see any movement of the motor... Particular to the SGL focuser project was that I never was able to move my motor in the absolute mode, while it did move (in the end) in relative mode (with step sizes around a couple of hundreds). And then there were other issues (like arbitrary behavior of the app regarding displaying of com traffic and updating the position, etc.). I'm sure that most of this was due to my ignorance, but in the end, I decided to try to write my own ASCOM driver. I'm on this at the moment...
Will keep you posted.
Pat