<http://schema.org/keywords>
"chrome os, citrix, esxi, hp, linux, mac, open source, parallels, solaris, sun, ubuntu, virtualbox, vmware, xen"^^<http://www.w3.org/2001/XMLSchema#string>
<https://www.virtualizationpractice.com/virtualbox-ose-3-0-still-a-viable-open-source-option-1245/>