There is a difference between Ubuntu for Android and using Ubuntu on android. Ubuntu through a loop file using chroot and (maybe) VNC is running Ubuntu (for ARM, technically). The Ubuntu for Android that I linked to is an addition to android that is something different - they may use a similar technique, but I don't think so, as from their description it sounds more native than that, and only runs through a secondary display (as many higher end phones have some kind of hdmi capability these days). In any case, near as I can tell, it is provided for phone manufacturers only at this point as something to include with their devices, and not something for the average joe (yet... I hope that will change).