It depends on which license you have. With either license you can install EW on any number of computers. With a Campus license you can activate any of them and use them at the same time. With a Single Projection license you can only activate and use one computer to display during a service. You can use the others without activation to create schedules, practice, etc. And if the main system goes out, you can activate one of those other computers temporarily while the main system is being repaired. The computers that aren't activated will be fully functional, but will display a watermark with the words EasyWorship across the screen. This is only when displaying the and is not embedded in any work you create.
Since you posted this in the EW6 Category, I'm guessing you're asking about EW6.
EasyWorship6 license came standard with a campus license, so you can install and register and project it on as many computers as you need at your church site, and including home computers to create schedules for your church.
Life Centre Church
Just wondering how things work re: licensing. We're a small church plant on the Sunshine Coast in Australia, and want to use a second laptop with easy worship on it just in case the primary laptop is unavailable that week (i.e., if the guy who brings the laptop suddenly can't make it). Are we allowed to have a copy of Easy Worship on two seperate laptops, where one is just the backup? We have only one service and operate only one projector in that service.