Simply,

One Powerbuilder license, any number of developed applications could be deployed.  

HTH

The runtime doesn't require additional licenses.

If you want to run a compiled application from a server (or any supported machine), then you prepare your application and deploy it. Runtime can be deployed in the same folder as your application, or to a "common" folder (in that case you need to deploy the xml that is created during compilation. This xml should point to the location where runtime is located). Take a look at the following link: Delivering your application to end users - - Application Techniques (appeon.com)

If you want to deploy using powerclient take a look at the information here: Working with a PowerClient project - - Users Guide (appeon.com)

Finally if your application is a cloud application using powerserver, this is the only case where you need to buy licenses, but for powerserver not for powerbuilder runtime.

Andreas.