You need a unique license for each of your servers. For developer machines you could use developer license valid for 1 year (free of cost), for test server you could buy a rental (commercial) license and for production server you could buy an Initial/additional (commercial) license.
Each license will be bound to either IP or Mac address.
From EPiServer 7 onward, you can bundle up all of your commercial licenses into one single config file (License.config) which you can use in your production,staging,test environments. For pricing and different kinds of commercial licenses, I recommend you to have a chat with your sales contact at EPiServer.
Hope it helps.
In order to get a developer license your company needs to be a partner?
What does being a partner mean?
Yes, you have to be attached with a partner company to get a developer license. However you can get a demo license (valid for 30 days) as well.
You as a partner company means, have .Net and EPiServer competence, EPiServer certified developers, actively selling and implementing EPiServer products. For more information, send an email to info at episerver dot com
How does licensing work in an environment with a production server, a test server and some developer machines?
Is a license required for each and everyone? If so, which licenses are needed?
Or is it possible to use the same license across the development environment?