Saying "This move could anger at least some open source enthusiasts" seems to imply that they're moving to a closed source or proprietary system, but Unity seem

Saying "This move could anger at least some open source enthusiasts" seems to imply that they're moving to a closed source or proprietary system, but Unity seems to be an open source project at a cursory glance. It could anger some Gnome enthusiasts, who are presumably open source enthusiasts as well, but not because of anything to do with the open source-ness of the project. Right? Or is Unity not quite as open as claimed?