I am running open source: version=7.0.0_GA_3077 release=20110127201852 builddate=20110127-2022.
I see this same thing. Resources are able to be double booked.
zmprov mc default zimbraCalendarResourceDoubleBookingAllowed FALSE
and then checked:
[$ zmprov gac -v |grep Double
When this didn't work, I tried restarting everything, but no luck.
I only use the default COS.
Any ideas on how to prevent double booking of resources ?