I looked a few free Point of Sales system, they all sucked so I had to write my own. Moving it over to MySql on week-ends. I like some open source, Apache is great, MySql is great, Linux sucks, used to be nice years ago but these days I don't like it at all. I think I'll give freeBSD at try next time I have a throw away cpu. Too bad System 5 (AIX) appears to be dead, that was a nice implementation of a Unix OS.
Do you mean the Linux kernel or are you referring to a particular distribution? I use Fedora on my laptops mostly because it is so easy to install, but I stopped using any distro for my servers quite a while back. I have used most of the major distributions at one time or another. These days, I usually build my Linux OS from source when I need it.
I have played around with freeBSD and OpenBSD a little bit. I find them to be kind of fun to play with when I need a hacker fix. I try to stay away from the BSD community, though. Linux has its share of whiners and crybabies, but BSD seems to be crawling with them.