Usermin is the user-facing portion of Webmin
Virtualmin is the module that ties them both together for ISP setups
Usermin and Webmin are GPL, Virtualmin is commercial (well there's an older version that's open source, but it's not nearly as good)
The best part about [User | Web | Virtual]min is that the whole setup is system friendly - it doesn't try to take over the system with custom packages, it doesn't mind hand-edited config files, etc.
Ok on a CentOS4 system, why on earth would SELinux be disabled if it's marked as 'permissive' in /etc/sysconfig/selinux?