We have the unlucky bonus of being "mastodon.radio" since 2018 and in the past it's been made to clear to other instances that they have to run mastodon to use the name in your domain or the trademark holders will request (legally) that you stop.
If I don't like something with mastodon what can I do?
How far can we stray from "pure" mastodon?
A fork without features we don't like?
A variant that is based on mastodon?
Complete rebrand, new domain, and different software?