The GNU Autoconf Archive is a collection of more than 450 macros for GNU
Autoconf that have been contributed as free software by friendly supporters
of the cause from all over the Internet. Every single one of those macros
can be re-used without imposing any restrictions whatsoever on the licensing
of the generated configure script. In particular, it is possible to use all
those macros in configure scripts that are meant for non-free software.

WWW: http://savannah.gnu.org/projects/autoconf-archive/