EDIT: This is mentality I find hilarious. It's either I can something for free or I can't get it at all. I think freedom in this case is about having something with little expended work.
There was no requirement to blacklist gab. Mastodon clients on f-droid are allowed let users use Gab.
What f-droid does not allow is apps preconfigured to connect to Gab, or who's primary purpose is to connect to Gab.
There was even a petition to have fdroid remove an app (fedilab) that had a blacklist to disallow Gab then removed it, claiming that removing Gab from the blacklist was specifically endorsing it, and there were some people who tried to claiming that not apps that were not blacklisting Gab when other apps did meant those apps primary purpose was to connect to Gab, but f-droid weren't having it: https://gitlab.com/fdroid/fdroiddata/-/issues/1736.
However, they did consider an app that was a straight fork tracking another with the only change being the removal of a blacklist to be disallowed.
That's cutting the hair mightily fine.
However, some fdroid users asked for its removal. They felt removing the blacklist feature, which had previously only blocked gab, was itself an endorsement of Gab and indicated the app's purpose was to access Gab since the other available mastodon app (Tusky) still had a blacklist.
fdroid did not agree and fedilab is still available.
OpenTusky was not allowed as it was literally Tusky with the server blacklist removed, created in response to Tusky blocking Gab. It also advertised this in the app description, so fdroid judged it to be primarily for accessing gab and removed it.
The "build your own if you don't like it" answer is often absurdly impractical, but not here. Someone who feels it's important can put up an alternate repo containing clients preconfigured to connect to Gab and even an alternate build of F-Droid preconfigured to use it in an afternoon.
Any mastodon app that refused to blacklist Gab got banned from F-Droid or something like that.
It is the perfect example of why I don’t even bother with federated projects. It’s just “wouldn’t it be great if _I_ were in charge?”
If that’s the situation, I’d rather Big Tech be in charge because at least they have some name recognition and hierarchy for decision making. Nobody cares if pizza-witches wrongfully broke terms. With Twitter at least peoples’ ears perk up.
In other words, there’s no rules in the alley. But there are rules in the town square.
[1]: https://reclaimthenet.org/f-droid-bans-gab-app/