With an adapter, the XBox controller (and other XBox peripherals) can be plugged into a PC or Mac's USB port. However, the XBox controller is not HID-compatible, so it is not usable by games or applications without a special driver. For some time, these drivers have been available for Windows and Linux. This driver is the first to support the XBox controller on Mac OS X.
This software installs a kernel extension (driver) that turns the XBox Gamepad into first-class HID citizen. Translation: it will work with any Mac OS X game/application that supports gamepads, including GamePad Companion and SimpleSoft's XGamePad software.
The full source code is available on the project website.