I never had pro on this machine and after an update I started getting this warning.
I tried to fix it with “# yum downgrade wbm-virtual-server-7.2-1.gpl-1 # service webmin restart”
It did not throw an error but the problem still persists.
Search the forums, this is likely due to a recent issue where @Joe accidentally released the Pro version into the GPL repo. This has been asked and answered a few times.