<A HREF="http://www.tenon.com/products/machten/"
  >MachTen</A> is a *(Unix)-like *(OS), a commercial version of 4.4_(BSD) using _(Mach) on 680x0 and PPC MacIntoshes.

There are free alternatives to it, like <A HREF="http://www.macbsd.com"
  >MacBSD</a>.
