Set NOxxx= before <bsd.own.mk> is pulled in (even indirectly).
Otherwise the appropriate MKxxx=no won't be defined .

MKfoo=no -> NOfoo

sample ftpusers with lots of examples on the syntax

convert from NOxxx= to MKxxx=no.
include <bsd.own.mk> if testing a MKxxx variable.

don't install in /usr/share if NOSHARE is defined

example ftpd.conf