Since Cloudmin is built on top of Webmin, un-installing it is simply a matter of removing Webmin and some additional modules. The commands for this on CentOS, Fedora or Redhat Enterprise are :
rpm -e webmin wbm-server-manager wbt-virtual-server-theme wbt-virtual-server-mobile wbm-security-updates
Or on Debian or Ubuntu, run :
dpkg --remove webmin-server-manager webmin-virtual-server-theme webmin-virtual-server-mobile webmin-security-updates
grep -v cloudmin.virtualmin.com /etc/apt/sources.list >/etc/apt/sources.list.tmp && mv /etc/apt/sources.list.tmp /etc/apt/sources.list
In both cases, any virtual systems created by Cloudmin will continue to run un-changed.
If you ever decide to re-install, systems that it used to manage can be re-imported using links under Add System on the left menu.