Clarify copyright/licensing (GPLv3+)

Clarify copyright/licensing (GPLv3+)

Need to go back through commit history and add copyright headers, but
the basic information is now there.

From: Adam Chlipala <adam@chlipala.net>
Subject: Re: Portal source license?
To: Clinton Ebadi <clinton@unknownlamer.org>
Date: Tue, 25 Feb 2014 08:35:37 -0500 (1 year, 12 weeks, 4 days ago)

I'm happy with any of the licenses you mention, at your preference.

On 02/21/2014 02:05 PM, Clinton Ebadi wrote:
> Greetings,
>
> I was dusting off the portal install and moving it over to navajos when
> I noticed that it does not have *any* licensing information
> attached. Luckily, no one but you, me, and bpt have touched it so fixing
> that should be easy.
>
> Do you have any opposition to licensing it AGPLv3+ or GPLv3+? Since it's
> a web service, I'd prefer AGPLv3+ (it doesn't appear to depend on
> anything that would make it burdensom to license it that way, and it's
> trivial to add a link in the footer to the git repo to satisfy the
> AGPLv3's source requirement), but since you wrote most of it... If you
> have some objection to the version 3 GNU licenses, GPLv2+ like domtool
> et al is fine by me as well.