If you read any technical mailing list for some of the more popular programs running UNIX, sure bet you'll find some flavor of Linux being mentioned....over and over again..
This is not to say that AIX or HP-UX or Solaris OS's aren't being used, but the sheer number of Sysadmins are choosing Linux as their OS dejure. I must admit that I'm not one of them. I use FreeBSD. Why one would ask?
Because the first UNIX server I put up in the 90's, was on an old 386 machine. And for some strange reason, it just would run SUSE and Slackware. Don't know why, but it wouldn't. So I opted to try BSDI, and have been a devotee of BSD ever since. I migrated to FreeBSD when BSDI had funding problems, and it was questionable whether or not the product would be supported.
I just did a quick search on www.linux.org for LINUX packages that are in English and work on an INTEL platform. I found 146 different distributions. If I ask for all distributions in English, I get 169; if I say just tell me how many different distributions there are, 191 flavors of LINUX pop up. Baskin-Robbins would be floored!
With all these versions of LINUX, and the four versions of BSD available (NetBSD, FreeBSD, BSDI and OpenBSD, the question that needs to be asked is why spend money for an operating system? Oh Bill! -- Oh Carly " Oh Scott, are you listening????