The decision was taken following a rift between Canonical and GNOME over certain design issues. "We were part of the GNOME shell design discussion, we put forward our views and they were not embraced by designers," Shuttleworth said at the ongoing Ubuntu Developer Summit.
"We took a divergent view from the GNOME shell folks on key design issues, for example how application menus should appear on the system, how one should search to find applications, [and] how one's favorite applications should be presented."
However, users will be allowed to install GNOME through Ubuntu’s software installation program. Natty Narwhal is scheduled to be released in April, 2011.