[waldemar72]

I tried to uncompress soft391.tar.gz and run it - same errors as described above. Same strange file names. IRIX 6.5.9m.

You have done something wrong! I checked twice archive I uploaded to google drive. Did you really uncompressed it as I told you! On your picture path to directory containing soft image files with strange names is wrong, (/Desktop/SI3D/SI3D39/SI3D39/IRIX/SOFTWARE ??). It's not path to extracted content to my archive!!! It should be /Desktop/temp/tars//irix/software !!! I also see your filenames are all in capitals and 8 letters long + 3 letters extension, so i think they were wrong extracted - it's DOS format!!! Since Softimage installation requires cdinst.dat (this is installation config file) and you have CDINST.DAT it refuses to install
Do everything again as I described above. Catalog structure you showed on your picture is not from my archive!!!
Do everything in console window!!! When you untar using command "tar -xvf soft39.1.tar" it verboses and shows in console window progress with extracting files it shows also absolute paths to extracted contents - go where it shows you - it should be /Desktop/temp/tars/irix/software !!!!