Why is FreeBSD so popular as the base OS for appliances? What makes it more attractive than other BSDs or, say, RHEL?
I would think the license.
I don’t know why, but I have always had the impression that FreeBSD was the most modern of the BSD systems. I feel like it has the most people working on it, would be the BSD most likely to support all of my hardware and would have the most up to date packages of all the BSDs.
I’m not really sure where I got that impression, but if other people also have that impression, it would explain why it’s popular for things like this.
This matches my experience. I’ve used OpenBSD and FreeBSD. The ports collection in FreeBSD is bigger and the community is bigger.
I once used PC-BSD and, as a dumb desktop user, it felt nearly indistinguishable from GNU/Linux. All the hardware worked and just about the same programs I was used to were there.
A focus on network performance?
Which kinds of appliances do you have in mind? In consumer-level stuff, at least, I think everything I’ve run into runs one or another kind of Linux. I haven’t done any kind of real survey, but the various wifi routers, set-top boxes, etc. I’ve owned seem to all be Linux varieties.
Some appliances that are FreeBSD based:
The PlayStation 4 reportedly runs Sony’s fork of FreeBSD, at least. I don’t know about other set-top boxes.
Apple AirPort Wi-Fi base stations have been based on NetBSD for quite a while (not sure if iOS has taken over yet or not).
OS X and iOS are based on some FreeBSD subsystems and APIs.
There’s a reasonable list on Wikipedia.
Looks like OpenBSD might be second judging by this comment from the Linux Azure guy at Microsoft. The comment is from 4 months ago and stated that FreeBSD is close and that they are looking into OpenBSD with 2 interested parties.
Hopefully the Hyper-V and OpenBSD situation improves as a result.