Yeah, and the KVM in illumos comes from a now obsolete Linux, and the pf in FreeBSD and Solaris comes from a now obsolete OpenBSD.
If anything, this should teach us not to port unportable things from different operating systems, because the maintenance cost is untenable.
Solaris' port of PF is not out of date. _And_ they are working with upstream to merge their changes so both parties have a) better code, and b) less maintenance burden.
iianm, Solaris has a port of IPF, not pf. Oracle is working on trying to port pf now.
The pf has been ported and it shipped already in Solaris 11.3. It is based on OpenBSD 5.5 code.