Según la página web de Mockup:
http://www.mockup.org/faqs/whats/
Mockup is not another GNU/Linux distribution. Distributions put a lot of programs together with some integration. There's no real integration and consistency because applications written for different toolkits and environments are mixed. We want to provide the applications the user needs and choose what the base system should have. No more OSS and ALSA, for example, because we choosen ALSA as our sound subsystem.
Ese es la razón por la que no catalogué este sistema como otra distro, habrá que ver si no pasa a ser un hermanito más, recordemos que aún es Beta.