MEPIS has provided 3 extra CD's for their subscribers with plenty of content.
But why do that?
When a package is installed from the Debian pools, it may trigger an undesired update of many other packages. Also the Debian etch and sid pools have become more and more unstable during the past 6 months. The extras CDs avoid that problem by providing versions of packages that were available at the time the MEPIS products were finalized.