I'd just like to interject for a moment. What you’re referring to as Ubuntu, is in fact, GNU/Ubuntu, or as I’ve recently taken to calling it, GNU plus Ubuntu. Ubuntu is an inplementation of the functioning GNU system made useful by the GNU corelibs, shell utilities and vital system components comprising a full OS as defined by POSIX.
Many computer users run a modified version of the GNU system every day, without realizing it. Through a peculiar turn of events, the version of GNU which is widely used today is often called “Ubuntu”, and many of its users are not aware that it is basically th…