From my understanding, uptodate is for Red Hats's .rpm and apt-get is for Debian's .deb packages, and Slackware uses the old .tar.gz/.tgz type of packages. Not really interchangeable, although, the .tar.gz/.tgz packages could be called universal if you don't mind the ./configure>./make>./make install routine that goes along with it. There is a tool called Alien that is used to install .rpm packages on a .deb based distro and vice versa.