I tried and it works with multiple users. I will say that problems of instability?
As I have stated in my posts, Compact SQL may work under Terminal Services as you are running instanaces of SambaPOS, so it see it as the local machine, and not a networked computer.
Even if it works, Compact SQL is designed only to run on a single computer and only for a single user. Using it on a Terminal Server may be unstable. Microsoft have not documented Compact SQL very well, and they have also not added sufficent protection to stop you from using it outside of its designed purpose.
Summary - USE AT YOUR OWN RISK in a multiuser environment.