I have found another metadata tool that is able to add or modify metadata to image files.
Exiv2 is a C++ library and a command line utility to access image metadata.
Developed for linux, it is nevertheless fairly portable. It is available as source code and also as executables for Windows and OSX
Source and executables for exiv2 can be downloaded from here http://www.exiv2.org/sample.html
There have been requests in the past for help in adjusting Camera Date and Time when someone has travelled to another timezone and taken photos without adjusting camera date.
This program allows the addition or subtraction of hhmmss from the exif timestamps
A typical use would be to run the command line
exiv2.exe -m changes01.txt C:/mytest/*
where the file changes01.txt contains the following lines
set Iptc.Application2.Headline "Paintings"
set Exif.Image.Artist "Vincent van Gogh"
This would result in setting these tags in all metadata capable files in C:/mytest
As usual, never run programs like this on original images, always use copies so you have a backup if you make a mistake.
I tried it and it works great for me.
I made a txt file to add artist and copyriht tags in a batch like way.
It works with the *.jpg option. So now i use it under Mandriva.
Thank you fot the hint.