/usr/lib/pd/extra/pdstring/LICENSE.txt is in pd-pdstring 0.10.2-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/pd/extra/pdstring/../../../../share/common-licenses/GPL-2
/usr/lib/pd/extra/pdstring/../../../../share/common-licenses/GPL-2