I see a lot of people on Twitter up in arms that there are “impostor” Mastodon accounts pretending to be them, rushing to report this “abuse” and decrying the criminality of reposting their tweets without their consent. It’s a bit confusing to people who are not familiar with the Fediverse, but I’ll try to clear it up.
Some people who get a Mastodon account choose to quit using Twitter. I’m not sure why people think this has to be an either/or choice when they can easily maintain both, but sure, do that if you like.
These ex-twitter folks sometimes still want to be able to see what certain people are saying on Twitter. Rather than signing into twitter to do that, they can ask a Twitter-to-Mastodon gateway to get the tweets for them and deliver them to their Mastodon feed.
There are a few servers in the Fediverse that provide this service. Most are named birdsite.xxx.xxx because the software is named Birdsite. All you have to do is subscribe to @twitter_username@birdsite.xxx.xxx and you will have a porthole out of Mastodon that can see the tweets of that user. This works for ANY twitter user. This is a connection directly to the actual feed from that twitter user, not pretending to be anything else, not inserting ersatz tweets, not stealing any identity.
To recap, Birdsite servers provide a service to Mastodon users allowing them to follow Twitter users. This service is also of benefit to the Twitter users as it gives them extended reach outside Twitter to the Fediverse while maintaining integrity of their identity and content.
As for the people complaining that these feeds are “unauthorized” or “rogue” or demanding “permission” be sought, I’m unclear why they tweet if not to be exposed to the widest possible audience. There seems to be a lot of comparison to re-publication of books or news articles, but I don’t follow the connection as tweets are not meant to be a scarce good so extending the range of a tweet does not reduce or impair the content provider’s ability to benefit, rather it improves it.
I will absolutely concur that there is a lot of confusion and the UI of a birdsite doesn’t do a lot to explain the situation clearly enough to stop non-technical, incurious or impatient people from jumping to nefarious conclusions.
Hope that helps.