PhpBB2 has "GPLv2 or later", and is compatible with both GPLv2 and GPLv3+.
PhpBB3 has just a link to GPLv2, and if the license is GPLv2 only, is incompatible with GPLv3+.
In phpBB2:
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/***************************************************************************
*
* 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.
*
***************************************************************************/
Code: Select all
* @license http://opensource.org/licenses/gpl-license.php GNU Public License