BE still requires "vStorage APIs for Data Protection" feature to be installed on the hypervisor.
Looking @ this link - http://www.vmware.com/products/vsphere/features-storage-api, "it states "The vSphere Storage APIs - Data Protection is included with all vSphere editions and kits." Possibly, the free edition includes this API. If it does, BE will be able to backup the VMs.
Hmm If you look at http://www.vmware.com/products/vsphere/compare.html
Which is a tab off the link that VJware posted it lists 3 VMware editions (Standard, Enterprise and Enterprise Plus)
As far as I am aware these are all licensed editions and not free and as such the "v-Storage APIs - Data Protection" may not be part of the free version and will definitely be needed for Backup Exec. - I don't think VMware call the free version an "edition"!
EDIT: Tip - do an internet search for VMware VADP and you will see that most backup products make use of it - although there are a few products that use other mechanisms that do not need it. However these products potentially have more cons than pros