Server 2008/12 Data Center retail activation?

Hi,

We're trying to figure out what we need to license upgrades from Win2003 to Win2008/12 and our sales rep isn't sure about one of our questions.  If we buy a retail Win2008/12 Data Center license (no SA or enterprise agreement), does that come with MAK C keys, use a KMS server, or some other mechanism to activate Windows VMs on a VMware host?  Or can you not use Win2008/12 without some form of SA agreement?

Thanks!