The Atrix 4G was one of the first Motorola devices to ship with its Webtop platform. When the phone is placed into its HD Multimedia Dock or Laptop Dock accessories, the user can access an Ubuntu-based desktop featuring access to the phone and its applications via the Mobile View application, integration of Android notifications into the desktop, multimedia playback through Entertainment Center, file management through Nautilus, and the Firefox web browser (along with support for Prism for the site-specific browsers used on Webtop mode).
I never knew it's "desktop mode" was Ubuntu and not Android.