As far as I know moxie, signals lead dev, considers only the use of the officially build and distributed client authorized to use their servers.

Moxie has resigned a few years ago. The article you linked to is 9 years old, Signal leadership has changed a bunch of times since. Signal can't detect that you're running an alternative client, because that check would require them to include some new code in the official client. Even if they did this, they couldn't just ban anyone who's client doesn't pass the check, since it could just be an older version of the official client. They could force everyone to use the official app, but they really have no reason to invest time and effort into enforcing this. Molly is only available for Android, and it isn't even on the Play Store or the official F-Droid repo, so the user base naturally won't be as big.

There was a period where they didn't push changes to the repo, but all the code was released afterwards and it's been getting regular updates ever since. But it also doesn't matter at all, since the Signal client is designed in a way that avoids putting trust in the server. Signal servers could literally be run by the NSA and it wouldn't matter, as everything is fully end-to-end encrypted, including metadata. The Signal protocol was also updated to use post-quantum cryptography in 2023.