Spent some time tracking down the Copyright URL and I don't seem to see it on the EXIF or IPTC lists on http://owl.phy.queensu.ca/~phil/exiftool/TagNames/ ... if this is still the correct resource to use, or if you even have control of this list, I don't know. Either way, for future searchers:
ExifTool Tag for Copyright Info URL is '-WebStatement' in the arguments and 'webStatment' for referencing the metadata output... so metadata['-webStatment']
Spent some time tracking down the Copyright URL and I don't seem to see it on the EXIF or IPTC lists on http://owl.phy.queensu.ca/~phil/exiftool/TagNames/ ... if this is still the correct resource to use, or if you even have control of this list, I don't know. Either way, for future searchers:
ExifTool Tag for Copyright Info URL is
'-WebStatement'in the arguments and 'webStatment' for referencing the metadata output... sometadata['-webStatment']