All ARIA-powered products use the same shared ARIA dynamic library.

So In one host, there is only one copy of it running in memory. Which will be the most recent version installed. All subsequently loaded ARIA "products" will then benefit for sharing of audio files and pools of various internal rendering resources.

So in short, there is the ARIA engine, there is the front ends (ARIA Player, Steinway, Garritan Instrument for Finale) and then you have the installed sound banks (GPO4, Steinway, etc.) which are available though the engine (since they are registered in the system registry/plists), in any of those front ends.