If you don't mind a bit of "constructive" criticism, I would have to ask why you want to run BSD (probably NetBSD) or Linux on these fine old HP workstations? Technically, they don't really have any useful purpose, other than keeping them running, and enjoying them, so why not keep HP/UX on them?
I say this as the owner of a Sun Ultra 5 workstation. Sure, it could run one of the BSD's or Linux on it, and keep more "up to date", but that would defeat the whole purpose of my acquiring this machine. By keeping it up and running Sun Solaris, I'm preserving it in it's original format.
I also plan on acquiring one of the older HP workstations, and if it comes with HP/UX, then that is what I will keep on it. If I can't get HP/UX on it, then I would consider running NetBSD on it.
Just my $0.02.