[getsat]

Plain FreeBSD has also had pf since 2003. OSX also comes with it.

[stock_toaster]

FreeBSD's version of pf is a tad old though (before new-format as I recall).

"""FreeBSD 8.X and prior is using the same version of PF as OpenBSD 4.1. FreeBSD 9.X and later is using the same version of PF as OpenBSD 4.5.""" [1]

[1]: http://www.freebsd.org/doc/handbook/firewalls-pf.html