I used FocusMax for years and it is a fine program but operates a bit differently than SGP focus. FocusMax is free so coming with the focuser is nothing special…
The Starizona focuser is not made by Starizona, but by a third party, I use a system sold by Starlight Instruments that is essentially identical:
The short version:
Focusmax uses a single star and V-curves generated ahead of time to do the focus.
SGP uses many stars in your FOV to do a V-curve each time.
With SGP, you use SGP’s focus method and do not have the option to use Focusmax. A number of other programs do use FocusMax to focus including ACP and CCD Autopilot. I have found SGP to be at least as accurate as FocusMax although Focusmax may have a slight edge if you are focusing thru a narrowband filter as it can adjust exposure time on the fly as well as slew to a bright star if need be.
I have found SGP focus to be less finicky and less likely to barf out, although Focusmax is not bad.
There is much more to it than the above but that is the short version.