The Download Assistant says “(recommended)” with Groove Agent, but when I start Dorico without it I get a warning message that Dorico needs Groove Agent to run…
(And this was when opening a file that uses the NotePerformer playback template, so Groove Agent would not have been used in the first place…)
It’s not compulsory, and you can turn off the warning, if you don’t think you’ll need it.