Well... I don't know that they ever officially released a protocol spec, but libpurple implements ICQ so at least enough of the protocol was reverse engineered or understood somehow to allow for OSS clients. So I suppose somebody could start from there and build a compatible server. Of course it might wind up only being compatible with Pidgin and other libpurple based clients, and the market for this is probably approximately 16 people worldwide. But still, it would be kinda fun.
What has happened to us that 16M people is something we just laugh at as an inconsequential number, wtf.
I literally meant 16 total people. To be fair, that was a bit of hyperbole, but the point is that there probably aren't a lot of people looking to use an "open source ICQ alternative" in 2024.
That doesn't mean that somebody shouldn't still do it, but it would probably be a passion project, more than something that would make money. At least that's my guess. :-)
When the Russians bought ICQ from the dying AOL and relaunched it, the same protocol was still available and Pidgin worked. But they turned it off after a while, and what a shock, everyone left.
I contacted the company, suggested they bridged it to other protocols, and pointed them at FOSS code that would let them do it. I got a snarky email back saying that what I proposed was impossible -- even though others had done it before. Idiots.
I have to admit, the thought has crossed my mind that it would be kinda cool to build a messaging server with support for ICQ protocol, MSN's protocol, OSCAR (AIM), Yahoo's protocol, etc. Maybe throw in XMPP too.
And in reading up on OSCAR[1] just now, I only just found out that ICQ did use OCSAR as well (at least according to Wikipedia). I never knew that. I had always thought OSCAR was only used by AIM.
