Dr Johnny Blanchard@drcaberry Fediverse is the underlying structure that Mastodon runs on. A bunch or other applications also run on the Fediverse.
Illi A. Hegerand for some BlackMastodon relates too much to huge instances like mastodon.social
BlackFediverse seems to relate more to the variety of instances
that being said, currently I see BlackMastodon being used more