Dear Forester developers,

Right now, the licensing of Forester's source code is a bit ambiguous: 
there is a `LICENSE` file in the repository, but there is no assertion 
(neither in the `README` nor in individual files) that any of the code 
is actually distributed under that license. (There is an appropriate 
line in the opam package manifest.)

The GNU Project recommends putting a license blurb in each source file. 
See: https://www.gnu.org/licenses/gpl-faq.en.html#NoticeInSourceFile

I propose to add to the top of each source file the following comment 
indicating the license:

     (* SPDX-License-Identifier: GPL-3.0-or-later *)


Any thoughts or suggestions? I also have to admit that I am a little 
puzzled about what to do in terms of copyright assignment. Perhaps we 
should ask future contributors to assign copyright to "The Forester 
Developers", but to go down that route, we must first secure such an 
assignment from prior contributors. Anyway, I am not a lawyer.

Best,
Jon