Downloading:
  http://www.libpng.org/
  http://libpng.sourceforge.net/

libpng is the original distribution, but with added
  Makefile.in libpng.ac withenable.ac

The directories
  contrib projects scripts
are not needed for teTeX and can be removed.

libpng is configured by libs/configure, so the (original)
libs/libpng/configure is not used by teTeX.
