The device is currently running Ubuntu and has a Webkit-based browser. Arrington originally wanted Firefox to run on the tablet. I’d be interested to see how Fennec works on the tablet. Fennec is designed to work well on mobile-class processors with tighter memory requirements. Fennec is also designed for touchscreens and supports the same add-ons mechanism as Firefox. Since Fennec is built on XULRunner, other XUL-based apps (Songbird, Chatzilla) get a free runtime.
Anyone with a Prototype B can test out Fennec Alpha 2 for Linux Desktop.