> it would be nice if I could download a binary version somewhere.
> does it exists ?
> 
> uname -a
> HP-UX adagio B.10.20 A 9000/899 614401342 two-user license
> 

If you can reach:

http://hpux.connect.org.uk/

you will find a gzipped depot file of the Ruby binary for 10.20.

Regards,
Barry