Free OS in the variety
At the mention of definition «the free software» to the majority of users, and at all only to "teapots", comes to at once mind Linux OS. However except it (Linux it not one system, and the huge family, sometimes few "relatives" similar at each other), are developed and quite vigorously less than two tens feel in any way, and even it is more, others free, free of charge extended, OS. The most known is FreeBSD, Solaris, Darwin which were less known - Haiku OS, React OS.
Any of these OS were developed in a subsoil of world scientific centers by means of grantovy support, and powerful international corporations invested in development of others. For example, Solaris was created by the Oracle company, and is primary as OS with the closed code though then the main part of a code was open and published. And here FreeBSD is the child of Berkeley university developed still in 1978 on the basis of free OC UNIX.
Decisions on the basis of UNIX, as we know, are very widespread and are actively applied in the various equipment, including the network. And servers on the basis of FreeBSD also still are applied and are, by the way, very reliable. The knowledge of it will not prevent even to the ordinary user – at least, for outlook expansion. And study at a leisure any operating system new to can to be it is useful, at least even that it will help to open unknown possibilities of «native Windows», to look at it from outside.