Michael Theodoulou has completed a binary installer package for the IRIX version of OpenOffice 1.0.1; see this Usenet thread for details. Many thanks go to Michael for his efforts in putting this together and sharing it with the IRIX community.
A few notes:
1. The current archive is mips-4 only.
2. You must set the DISPLAY environment variable prior to installation, i.e.:
setenv DISPLAY koyori:0.0
Failure to set this variable will cause the installer to freeze during the copying phase and subsequent lauches of the installed application will also fail. Adding the environment variable to the shell startup file is the best long term solution.
3. Execute the 'setup' program from the installation directory, choose 'Standard Installation' and click Ignore for any files the installer claims are missing.
4. Start OpenOffice via ./soffice in the destination directory.
Additional IRIX specific installation instructions can be found here.
General information on OpenOffice can be found at the official web site:
Download:

