Griff was designed for the Microsoft PocketPC platform. Here's a list of compatible operating systems: In short, Griff is compatible with every PocketPC based device. Microsoft have done an amazing job of maintaining compatibility whilst changing the operating system.
HOWEVER Griff was designed and optimised for the screen dimensions of the original PocketPC, 240x320, otherwise known as QVGA. Since then, devices have appeared with square screens, landscape screens and vga. Although Griff will run on these devices, the display may be compromised.