Knighn includes potrace 1.16, a separate program that Knighn runs to trace
pictures into vector shapes. Knighn does not change potrace or link it into
its own code.

potrace is Copyright (C) 2001-2019 Peter Selinger and is free software under
the GNU General Public License, version 2 or later. The licence is in the
file COPYING next to this notice.

The complete source code of this copy of potrace is the unchanged release
archive potrace-1.16.tar.gz, which is next to this notice. It is also at
  https://potrace.sourceforge.net/download/1.16/potrace-1.16.tar.gz
  SHA-256 be8248a17dedd6ccbaab2fcc45835bb0502d062e40fbded3bc56028ce5eb7acc
It was built with:
  ./configure --disable-shared --enable-static --with-libpotrace=no
