How did the Unix/Linux site survive Area51? I've seen several proposals closed as dupes of existing sites, but from my first look at the Unix/Linux FAQs, it seems that site could just be split into askubuntu.com, Apple, and Android Enthusiasts. Was the Unix/Linux site first?
I'm not sure what Joel is talking about, but Unix/Linux was proposed two weeks before Ubuntu was. Ubuntu went through definition/commitment faster and went into beta two weeks before Unix/Linux. There was much discussion about why they were separate. Robert mentioned that:
It was inescapably clear that a site about 'Linux' simply held no interest to a very large group of users who identify themselves as 'Ubuntu users.'
and an Ubuntu user commented that:
Ubuntu has a large enough audience to warrant being treated separately
That was months ago and is pretty fixed at this point;
as I understand it Ubuntu handles Ubuntu questions and Unix/Linux handles the rest, although I don't think it actually works out that way in practice the sites ended up deciding to only migrate from Ubuntu to Unix if the question doesn't apply to Ubuntu, and only from Unix to Ubuntu if the question doesn't apply to any distro but Ubuntu.
I definitely don't agree that "that site could just be split into askubuntu.com, Apple, and Android Enthusiasts" -- you can't split all Unix/Linux questions into questions about Ubuntu, Apple, or Android devices; that's a tiny fraction of the total possible questions.
There isn't that much overlap between Unix.SE on one hand and Ubuntu.SE, Apple.SE and Android.SE on the other hand. At the moment, about 2% of the questions on Unix.SE are tagged
osx and 7% are tagged
ubuntu. (None are tagged
android.) So 90% are either off-topic on the other sites or generic enough that a more general site is a better home for them.
Even when there's an overlap between the sites, the focus tends to be different. You're more likely to get an answer with a screenshot of the official GUI on Ubuntu.SE, and an answer that's reusable on any Linux distribution on Unix.SE. Even though the topics overlap, the audiences tend to be different.
The sites that Unix.SE might drain audience from are Super User and Server Fault. Yet there's little overlap between the high-rep users on Unix and the high-rep users on on SU and SF. I'll let others explain that part as I'm part of the overlap, but I do find that it's hard to filter unix questions on SU and SF. There's certainly no easy set of tags (not to mention that SU has a lot of poorly-tagged questions).
At the time that Ubuntu was being proposed, a group of Unix fans thought Ubuntu was too parochial and there should be a more ecumenical Unix/Linux site. Now we have both.