FreeBSD is the second BSD to come in the early 90s. Its traditional home architecture is x86, though it also runs (or is beeing ported to) on Alpha, amd64, ia64, MIPS, pc98, PPC and sparc64. Despite the fact that of the *BSDs it's probably closest to a typical LinuxDistribution, which are typically SysVish, it feels very much like a BSD system. Naturally, as all BSDs are, it too is under BSDLicense.
See also FreeBSDNotes.