Maybe this will help clarify some things. Or not, who knows!
Machines that are running BRUSH rotaries can have the BRUSHLESS servo drive just like the x,y, and z axis. However, there is a transformer assy bolted to the inside bottom of the electrical cabinet which converts everything to DC. On this machine you will have a single connector plug on the outside of the electrical cabinet for connecting the rotary.
Newer machines set up for BRUSHLESS rotaries will have 2 cable connectors on the outside of the cabinet and utilize the same BRUSHLESS servo amps inside to power the rotary.
Both types of machine setups will utilize the same/similar BRUSHLESS servo drive card.
To run a BRUSH rotary (1 plug) for a machine configured for BRUSHLESS (2 plugs) rotary, you must use the converter box that Machenit2 has detailed.