Licensing of Autoconf

[Jack Pearson]

Hello all! Thanks for all the great work you do.

I was browsing the GNU Autoconf repo and became rather confused about what the 
license is for GNU Autoconf.

File copyright headers say that the project is licensed under GPLv3+. However, 
the project website (http://savannah.gnu.org/projects/autoconf) says that it's 
licensed under GPLv2+.

I'm inclined to believe the copyright headers, but the main COPYING file is 
GPLv2. Is this significant?

Thanks,
Jack