/usr/share/doc/virtuoso-opensource-6.1/CREDITS.gz is in virtuoso-opensource-6.1 6.1.6+repack-0ubuntu9.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/virtuoso-opensource-6.1/../virtuoso-opensource-6.1-common/CREDITS.gz