webCDwriter uses the command line tool mkisofs to create ISO9660 CD filesystems. If you want to use non-ISO-8859-1 characters in file names, there is a patched mkisofs with UTF-8 support available.
You may install a new mkisofs for webCDwriter by the following commands:
cp -af mkisofs @mkisofsInternalPath@ chown root.@GROUP@ @mkisofsInternalPath@ chmod 4750 @mkisofsInternalPath@
Afterwards reload the configuration.