Don't let the name fool you. PC Linux OS is just another Linux distribution, but you do have to pay for it if you'd like to use it. Ubuntu is a whole other distribution unto itself. Basically, the only way Linux distributions are grouped together are based on the packaging system. For example, RedHat and Fedora use .rpm so you could say that they are alike whereas Debian and Ubuntu are based on .deb packages.
It says PCLinux OS, but I thought thaty wasnt a distrso nut rather a grouping, ex Ubuntu would be part of PC Linux OS since its for PC!!