Although I have no authority to represent the FreeBSD Foundation, I will
say that FreeBSD has been using clang for some time now. FreeBSD is a
Unix operating system that was initially developed by the University of
California at Berkeley and is based on BSD4.4-Lite. It's different than
Linux because FreeBSD is a complete operating system. Initially, gcc
was used, however FreeBSD changed to clang as the default system
compiler about two years ago. The website can be found at
http://www.freebsd.org. The current version of clang (as of FreeBSD
10.2) is 3.4.1.
