/usr/share/proftpd/templates/dnsbl.conf is in proftpd-mod-dnsbl 0.1.5-4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/proftpd/templates/../../doc/proftpd-mod-dnsbl/dnsbl.conf
/usr/share/proftpd/templates/../../doc/proftpd-mod-dnsbl/dnsbl.conf