BUG #17169: Does PG involve GPL license?

The following bug has been logged on the website:

Bug reference:      17169
Logged by:          Bo Chen
Email address:      bchen90@163.com
PostgreSQL version: 11.13
Operating system:   euleros v2r7 x86_64
Description:

Hi, all

    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. 
   We analyzes the comment of copyright in the file head. For files in
config dir, it seems our using is GPL exceptional. But I can't confirm my
understanding is correct or not？

    Best regards

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