I'm guessing that you are right, and somehow it can be made to run on SBS without admin privileges
It can be difficult to log into an SBS computer with non-admin privilegs. It's complicated. Not sure about Essentials.
I will say I installed it to VMWare. Gotta love the client backups. Somehow, it always finds it's way onto my domain, which is a big no no with SBS. Only one domain allowed.
That's another good thing about SBS 2011 Standard with Premium Add-on. You can run more than one domain. That's when it gets really interesting.
So, I ran eMedware on 2011 Essentials as an admin. Not as a user with non-admin privileges. It worked fine, but I don't know if it were the same thing.
