Yeah I checked the project out too. The microstepping is done by the onboard stepper driver chip James. However it only supports 8th stepping.
Also the coarse timer resolution means there is a limit to how many speeds it can run at, where the Linistepper code I posted for Ceefnas project will do 12th stepping, and uses a very high resolution Bresenham system for timing so it can do practically any speed with great precision.
And I probably should mention the linear driving of the motor current by the Linistepper means the stepper can move very smoothly (ie "stepless") at a tuned speed. An 8th step chip based driver is going to be a bit gritty for telescope use.