FM or HD/DAB/streaming
For ST-Enterprise, we have a very simple license mechanism, that gives you access to all the features that can be licensed separately in Stereo Tool, such as Declipper, Delossifier, Advanced Dynamics, Advanced RDS and The BIMP. They also contain Nielsen PPM watermarking (you need a license from Nielsen as well though).
FM processing instance offers you all the features that you need for an FM station. An FM processor can generate FM and non-FM signals at the same time, so you can use a single FM license to process for both FM and HD/DAB/streaming, for example.
HD/DAB/Streaming/TV/AM instance offers everything except FM processing.
Since each instance has its own license key, you can combine different license types on a single ST-Enterprise system.