pikchr-sys includes the C89 source code from Pikchr. Pikchr licence:

   Zero-Clause BSD license

   Copyright (C) 2020-09-01 by D. Richard Hipp <drh@sqlite.org>

   Permission to use, copy, modify, and/or distribute this software for
   any purpose with or without fee is hereby granted.

   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
   SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
   IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
