Introduced in 1991, Linux boasts an estimated 67 million users worldwide according to linuxcounter.net. Free versions abound, but companies adopting Linux as part of critical infrastructure typically require more support than a community of unpaid, albeit enthusiastic, volunteers can provide.
The five products we tested -- SUSE Enterprise Server 11 Service Pack 2, Mandriva Business Server 1.0, ClearOS 6 Professional, Red Hat Enterprise Linux 6.4 and Ubuntu 12.04 LTS -- are all enterprise server versions offering commercial support options, either at the OS level or in the form of commercial management tools and support plans.
For enterprises, the advantages of going with commercial support options include LTR (Long Term Release) versions of the software, improved interoperability, application support and legal protection if A a portion of the open source software is found to infringe on third-party intellectual property rights. Also, vendor longevity is more likely with a Linux distribution that's backed by a commercial revenue stream.