Allows you to login using phpbb3 credentials. It loads the bare minimum of phpbb3 to start the authenticiation process.
Inside the simplesamlphp module directory, run:
git clone https://github.com/Unvanquished/simplesamlphp-phpbbauth.git phpbbauth
Then, in config/authsources.php, add
'phpbb3' => array(
'phpbbauth:Auth',
'phpbb_root' => 'PATH TO PHPBB3 ROOT',
),