Legal question on Bing Wallpapers

Is it legal to use Bing Wallpaper on Linux, using tools available there, like Gnome plugin "Bing Wallpaper" and such? Would it be legal for Ubuntu to add it directly in the distro (not images, those are obviously copyrighted by Getty et al, just the tool that downloads it daily) ? I tried to figure this from terms of use, but it is really hard to understand what is actually allowed.