COPYING file looks reporting GPLv2 license.
If the software is licensed under GPLv2, you can't report GPLv3+ license
only with License tag.
At the end of COPYING file it says:
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.