Years ago us SGI hobbyists were able to talk to SGI
about this and a huge problem SGI had with any kind of hobbyist
license for IRIX or turning it free is it's fully of licensed 3rd party stuff. But
maybe now that's it's expired, or all
the companies things were licensed from are gone.
Release of Classic HP3000 died for the same reason from the same company.
HP has no motivation to spend time/money to release this. Also, the only way CHM
was able to release what we did (HP1000, 68K 9000 and Apollo) was having
us release it only for non-commercial research/hobby purposes.