AntonioRocco would be the best person to ask. He works for KRCS who are an Apple Premium Reseller/Solution Expert in the U.K.
Mac App Store on your Xserve running Snow Leopard Server it will prompt you to buy Lion Server at the same time.
The terminal access point in the EULA seems a little odd giving that one of Lion's selling points is it now has multiple VNC connections allowed at one time.
Is this not a form of terminal sessions?
Ive just given them a couple of old imacs to use for keynotes to keep them happy. Not wasting any more of my time on them ;p
I work with Tony at KRCS and my view on this is in the EULA Apple trying to stop dealers from setting up terminal service agreements for end users. I don't think Apple would care in the least if you set up a Lion Mac to run two instances of Keynote on.
I have plenty of education customers using loads of remote services on Macs that may violate the UELA....