ICQ, AIM, MSN Messenger, PawWaw, Yahoo Messenger, Odigo, (and 30 more names I can't remeber) - there was a huge instant messaging war, the first stage of which was decidedly won by AOL (with AIM and the purchase of ICQ), but Microsoft later made great headway through sheer monopoly force and persistence - but that eventually became irrelevant with SMS taking over as the main form of instant messaging and then WhatsApp taking the world by storm.
None of this was open source. Not a single one of the successful messengers. In fact, AOL fought alternative clients fiercely all the time, and Microsoft started fighting them as soon as they got non-trivial market share.
What about XMPP (Which started life as Jabber before being standardized?)? Well, that one is open source. But it only survived and flourished because all the commercial outfits were busy fighting each other.
I was tangentially involved with the failed instant messaging standardization process at the turn of the millennium, and Jabber was by far the worst technical proposal at the time -- but the process was political, and when the committee disbanded due to all the political infighting, Jabber, which didn't have the commercial interests, was the remaining option.
I'm actually contemplating ICQ, it's still around and looks no worse than any other service. Matrix might be a better solution though, it's federated and open. https://matrix.org/blog/home/