not a great problem .. I can't remove "Orage", neither with GSlapt [not shown] nor with slapt-get --remove orage, orage-4.6.1, Orage or Orage-4.6.1 .. "package not installed" ... But - it's there an running
Slackware (and thus Salix) consolidates some things into larger combined packages. So xfwm4 for instance is part of the xfce package, whereas it would have its own package in Debian/Ubuntu.
You can remove the parts of the xfce package you don't want, e.g. the parts related to orage. If you don't delete anything wrong, this is perfectly fine with the package management. Reinstalling or upgrading the package restores the files again.
Look at /var/log/packages to determine the files of the xfce package, that you don't want.