Compiz is now working well with KDE3. Compiz with KDE3 windows decorator enabled is added to KDE3 repository. It has the same version as Compiz in OpenSUSE 11.3 so under this release you only have to install compiz-kde3 package in addition to the compiz from the main repo. The settings will be the same under KDE3, Gnome and KDE4.
To easily enable and manage Compiz I suggest to install fusion-icon package which is available in private repos in OBS.