XBPS includes the following software from third parties for
internal use in the code:

- queue.h from NetBSD: include/queue.h.

- relational dewey version matching code from NetBSD:
  lib/external/dewey.c

- strlcat and strlcpy functions from OpenBSD:
  lib/compat/strlc{at,cpy}.c

- humanize_number(3) from NetBSD: lib/external/humanize_number.c

- mkpath from NetBSD's mkdir(1): lib/external/mkpath.c

- fexec from NetBSD's pkg_install: lib/external/fexec.c

- libfetch-2.34 from NetBSD (pkgsrc/net/libfetch): lib/fetch

- portableproplib-0.6.8 (lib/portableproplib) from
  https://github.com/xtraeme/portableproplib

- uthash-2.1.0 (include/uthash.h) from
  http://troydhanson.github.com/uthash/