Quoting IT Jungle
Years ago, the Linux operating system stole the open source show and arguably the hearts and minds of the IT industry--or at least those parts of the industry that are inclined to support and use open source software. But with the advent of OpenSolaris a year ago as an open source Unix implementation, Linux is no longer the only option. And, it never was. There are three major BSD Unixes out there, and a number of others, and they are innovating, too.
(Let's not forget that Solaris is itself a variant of BSD with a lot of AT&T Unix SVR4 thrown in for good measure, and Apple's Mac OS X Server is also a BSD variant.)
The FreeBSD variant of the BSDs is probably the best known, and although it is difficult to get any hard numbers concerning BSD installations, FreeBSD is probably the most widely distributed open source Unix. (Although, with 5 million installations, Solaris 10 can probably grab that mantle now, and if not now, then soon.)
Over at the NetBSD project, the coders behind the project were early adopters the open source Xen virtual machine hypervisor from XenSource, and supported Xen 2.0 as a hypervisor within NetBSD. (The FreeBSD project is also working on a Xen port.) This week, the project announced NetBSD 3.0.1, the first security/critical patch release of its 3.0 tree, and also said that the Xen 3.0 hypervisor can work below NetBSD 3.0. This brings NetBSD on par with the new SUSE Linux Enterprise Server 10 from Novell, which was announced two weeks ago, and about six months ahead of where Red Hat will be with Xen support when--and if--it delivers its Enterprise Linux 5 update in December.
Read the entire article, here.