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I would be very wary about running the smeplus update script. You may affect the ability to smoothly upgrade your server to newer versions of sme later.
It does not really update your server with security bugs & fixes, only, as such, but it adds new programs & rpms that may not be already installed to get additional functionality and the latest versions of those programs.
If you need to apply "updates" from that script, then be selective and only apply what is strictly needed eg php update which does have some security issues if you use php apps.
If you have the Mitel v6.0 release, there is very little difference between that and the contribs.org 6.0.1 release, essentially they are the same, and as far as I understand it are secure if you have not done further customisations to your server.
Did you apply the Mitel updates for v6.0 which do add security fixes etc ?
ftp://ftp.ibiblio.org/pub/linux/distributions/e-smith/updates/6.0/RPMS/You can safely continue using sme v6.0 as long as you have applied the Mitel updates, and assessed php security requirements.