I'm not talking about the EULA, I'm talking about some sort of deal that was made a while ago, to run it on Oracle's servers.
I can't for the life of me remember where I read it, and I might even be wrong.
And like I said, what you're trying to remember has something completely bogus is Apple agreeing to license Leopard Server to run in a VM on Apple branded hardware :
http://blogs.vmware.com/vmtn/2008/01/virtual-leopa-1.html
So Leopard Server works in a VMWare environnement. A simple license change will enable anyone with a ESXi environnement to run OS X Server.