Update to CC License 4.0

You can edit the plugin and change in the file ccg-admin.php the lines

$banner = "<a target='_blank' rel='license nofollow' href='https://creativecommons.org/licenses/" . $attributes . "/4.0/'><img alt='Creative Commons License' style='border-width:0' src='https://i.creativecommons.org/l/" . $attributes . "/4.0/88x31.png' /></a><br />";
	$islicensed =  ' is licensed under a <a target="_blank" rel="license nofollow" href="https://creativecommons.org/licenses/' . $attributes . '/4.0/">' . $attributes_text . ' 4.0 International</a><br />';