BUG #17169: Does PG involve GPL license?

PG Bug reporting form <noreply@postgresql.org> writes:

Recently, We planned to use PostgreSQL for owner project, so we
retrieved the license of all PG source code. And the following files which
involve the GPL and perl copyright license.

config
ax_pthread.m4
check_decls.m4
config.guess
config.sub
libtool.m4
pkg.m4

Those files come from autoconf (they are part of the source code that
goes into the configure script). The autoconf manual says, in its
FAQ section:

20.1 Distributing `configure' Scripts
=====================================

What are the restrictions on distributing `configure'
scripts that Autoconf generates? How does that affect my
programs that use them?

There are no restrictions on how the configuration scripts that
Autoconf produces may be distributed or used. In Autoconf version 1,
they were covered by the GNU General Public License. We still encourage
software authors to distribute their work under terms like those of the
GPL, but doing so is not required to use Autoconf.

Of the other files that might be used with `configure',
`config.h.in' is under whatever copyright you use for your
`configure.ac'. `config.sub' and `config.guess' have an exception to
the GPL when they are used with an Autoconf-generated `configure'
script, which permits you to distribute them under the same terms as
the rest of your package. `install-sh' is from the X Consortium and is
not copyrighted.

regards, tom lane