A quick look reveals they are using 4 PWM’s for the Adjustable Frequency Motor output (1 for each motor), 2 PWM’s for servos, and reusing the 4 PWM’s for stepper control, along with some I/O for shifting data to relay’s for direction control on the motors.
You would need to port the library by combining the .h and .cpp files all together with your application.cpp (the sketch), and put that into the Sparkulator (Spark Build, aka Cloud IDE, aka Web IDE aka Spark IDE). This would be possible!
The Spark Core has 8 PWMs, which can be used to control Servos or just used as general purpose PWM outputs. By default the gen purp PWM is fixed at 500Hz. I came up with a way to set them to whatever you want (tested up to 64kHz).
This, coupled with a bunch of chopping to the #defines AVR / PIC32 / etc… and the library should be working.
That said, you need the pins that have this hardware functionality to couple to the pins of the shield that need that functionality. Since the Core has more PWM’s than the Arduino, you should be in good shape, just need to check.
If you want to take a stab at it… please do! Otherwise I could try to port it maybe this weekend. Wish I had a motor shield though to test it