COPYING better explanation for GPL versus LGPL

[Paul Eggert]

I installed this in gnulib to help explain the copyright issue a bit
better.

2006-10-26  Paul Eggert  <address@hidden>

        * COPYING: Explain how gnulib-tool converts licence headers.
        Almost all wording by Eric Blake.

--- COPYING     15 Sep 2004 15:59:43 -0000      1.2
+++ COPYING     26 Oct 2006 16:20:28 -0000      1.3
@@ -1,7 +1,17 @@
-$Id: COPYING,v 1.2 2004/09/15 15:59:43 karl Exp $
+$Id: COPYING,v 1.3 2006/10/26 16:20:28 eggert Exp $
 The files in here are mostly copyright (C) Free Software Foundation, and
 are under assorted licenses.  Mostly, but not entirely, GPL.
 
+Many modules are provided dual-license, either GPL or LGPL at your
+option.  The headers of files in the lib directory (e.g., lib/error.c)
+state GPL for convenience, since the bulk of current gnulib users are
+GPL'd programs.  But the files in the modules directory (e.g.,
+modules/error) state the true license of each file, and when you use
+'gnulib-tool --lgpl --import <modules>', gnulib-tool either rewrites
+the files to have an LGPL header as part of copying them from gnulib
+to your project directory, or fails because the modules you requested
+were not licensed under LGPL.
+
 Some of the source files in lib/ have different licenses.  Also, the
 copy of maintain.texi in doc/ has a verbatim-copying license, and
 doc/standards.texi and make-stds.texi are GFDL.