The Matrix screen saver is part of the KDE3 repository. I normally add these two to my repository list:
http://download.opensuse.org/repositories/KDE:/KDE3/openSUSE_11.3/
http://download.opensuse.org/repositories/KDE:/Community/openSUSE_11.3/
Then I load up Software Management and search for screen. I then load/install kdeartwork3-kscreensaver & kdeartwork3-xscreensaver. You may need to log out and back into KDE to see the new screen savers as being present after the installation.
Thank You,