I am looking for the software for HP64000 development system. Our compilers and assemblers which run on HP-UX were missing. So, we have to dig for them now.
You're aware that if you don't have a license than approaching HP may be your only legal alternative...
However, it appears that this is 30 year old hardware, so your best bet may be to look for sites dedicated to HP hardware (try http://hpmuseum.org/ for a start) as they sometimes have access to software that HP may have granted to them. You'll also probably find more people there with specific information.