So you have a developer license that allows you to develop software for all facilities that hire you to do it and the customer buys the considerably cheaper Runtime licenses to be able to run the software you wrote for that process.
Some sites will want to have a developer license to avoid having to go outside for minor modifications and they'll then buy a developer license as well for a single node (usually an engineering station).
The company should decide if they want a developer license... and then buy the runtime licenses for all sites in one go to perhaps cut down on cost.