Derivatives of Ubuntu
Ubuntu is designed to be a solid foundation for creating further derivatives. In the case of the official derivatives, all the packages used are from the main Ubuntu repositories, so a user from any variant can seamlessly install packages from any other, and even convert completely to a different variant.
Kubuntu
Kubuntu is a user friendly operating system based on KDE, the K Desktop Environment. Kubuntu and Ubuntu are not meant to be seen as distinct projects; Kubuntu is part of the Ubuntu project, and they are both part of one development team that contributes to the whole. Kubuntu is Ubuntu with a different default set-up, the Ubuntu CD contains only GNOME as a desktop environment; the Kubuntu CD contains only KDE, this is the primary difference.
