This is normally not possible. Uniprint was designed with a Domain or Enterprise environment in mind. When building the PopUp package, it's built with the server name that's entered in Pharos, and if that's not resolvable, it won't print, and PopUps will not have the ability to function as desired.
However if your DNS is configured such that clients outside your Windows Domain can resolve IP's to host names that re inside your Windows Domain then potentially they may work. Networking and routing also play a big factor in the communications between the Pharos Popu Client and the Pharos Server components.