webCDwriter uses the command line tool cdrdao to copy audio CDs.
You may either disable (don't forget to save the change)
or install a cdrdao for webCDwriter by the following commands:
cp -af cdrdao @cdrdaoInternalPath@ chown root.@GROUP@ @cdrdaoInternalPath@ chmod 4750 @cdrdaoInternalPath@
Afterwards reload the configuration.