Hi Robert!
The website then opens in the same window as the forum. If all extern websites are to be opened in new windows, then you have to do this in the GenericBoards.template.php:
Search:
<a href="', $board['href'], '" id="b', $board['id'], '">', $board['name'], '</a>';
Replace with:
<a', $board['is_redirect'] ? ' target="_blank"' : '', ' href="', $board['href'], '" id="b', $board['id'], '">', $board['name'], '</a>';