My biggest hold-up with that sort of work is that Facebook has previously threatened to ban users who use third-party clients, and then they have gone through with the threat. Is this no longer the case?
Meta also threatened app makers to start a lawsuit. Whatsapp Plus, Whatsup and Mitakuuluu people stopped on that threat. I don't see a reason why Meta would change their stance on this.
There is now a law from the EU, I think it is the DMA, which could change things for people living in the EU regarding interoperability. I haven't read anything about practical follow-ups yet.
By the way, only releasing source code as a blueprint might be fine, that happened before. I might remember it wrong, but it might be lame, the mp3 encoder.
Has a well-behaved third party client ever been an issue?. A third party client that does things like retain deleted messages, report that read receipts are enabled but never actually sends them or other 'anti-social' behaviors is definitely asking to get banned.
[1]: In July 2021 Facebook sent the developer of Unfollow Everything a cease-and-desist letter because he made a browser extension which helped people use Facebook less.
[2]: In 2020, Facebook shutted down the NYU Ad Observatory by shutting down the Facebook accounts of Cybersecurity for Democracy team members Damon McCoy and Laura Edelson.
I can't speak for everyone, but I've been using WhatsApp since ~2010, mostly the official client but with bouts of unofficial client usage, and I've never been banned.
Probably not very detectable for Meta since it uses a wrapped webview, but I've been using ZapZap on Linux for a good while now and I haven't seen a ban yet.
if something can happen and haven't happened to you, doesn't warrant a comment i believe. it doesn't help much to figure the data points for the cases were it does happen, since it's implied everyone to whom it have happened would have lots of opportunities to post comments it never happened before.
