bbPress.org

Ok I find a way but I am not happy about that but it works….
You can see live here : http://sakifo.gamers.re/forums/

If someone have a better solution, I put that there :

<?php
/**
 * Forums Loop
 *
 * @package bbPress
 * @subpackage Theme
 */
?>

<?php do_action('bbp_template_before_forums_loop'); ?>

<?php
if(bbp_get_forum_id()){
   ?>
<ul id="forums-list-<?php bbp_forum_id(); ?>" class="bbp-forums">

	<li class="bbp-header">

		<ul class="forum-titles">
			<li class="bbp-forum-info"><?php echo bbp_forum_title(); ?></li>
			<li class="bbp-forum-topic-count"><?php _e( 'Topics', 'bbpress' ); ?></li>
			<li class="bbp-forum-reply-count"><?php bbp_show_lead_topic() ? _e( 'Replies', 'bbpress' ) : _e( 'Posts', 'bbpress' ); ?></li>
			<li class="bbp-forum-freshness"><?php _e( 'Freshness', 'bbpress' ); ?></li>
		</ul>

	</li><!-- .bbp-header -->

	<li class="bbp-body">

		<?php while ( bbp_forums() ) : bbp_the_forum(); ?>

			<?php bbp_get_template_part( 'loop', 'single-forum' ); ?>

		<?php endwhile; ?>

	</li><!-- .bbp-body -->

	<li class="bbp-footer">

		<div class="tr">
			<p class="td colspan4">&nbsp;</p>
		</div><!-- .tr -->

	</li><!-- .bbp-footer -->

</ul><!-- .forums-directory -->
<?php
}
else {
?>

<?php while ( bbp_forums() ) : bbp_the_forum();?>
<?php
    /* We print the header only if we want to show a category or if it's the first item of a no-parent forum list */
    if (bbp_is_forum_category() OR ! $bbp_forums_noheader) {
        ?>

        <ul id="forums-list-<?php bbp_forum_id(); ?>" class="bbp-forums">

            <li class="bbp-header">

                <ul class="forum-titles">
                    <li class="bbp-forum-info">
                        <?php if (bbp_is_forum_category()) { ?>
                            <a class="bbp-forum-title" href="<?php bbp_forum_permalink(bbp_get_forum_parent_id()); ?>">
                                <?php bbp_forum_title(bbp_get_forum_parent_id()); ?>
                            </a>
                        <?php } else {
                            _e('Forum', 'bbpress');
                        } ?>
                    </li>
                    <li class="bbp-forum-topic-count"><?php _e('Topics', 'bbpress'); ?></li>
                    <li class="bbp-forum-reply-count"><?php bbp_show_lead_topic() ? _e('Replies', 'bbpress') : _e('Posts', 'bbpress'); ?></li>
                    <li class="bbp-forum-freshness"><?php _e('Freshness', 'bbpress'); ?></li>
                    <li class="bbp-forum-freshness-avatar"></li>
                </ul>

            </li><!-- .bbp-header -->
    <?php } ?>

        <li class="bbp-body">

            <?php
            /* If the forum is a category, we're gonna make another loop to show its subforums and sub-subforums as if those were forums */
            if (bbp_is_forum_category()) {

                $temp_query = clone bbpress()->forum_query;
                bbp_has_forums('post_parent=' . bbp_get_forum_id());
                while (bbp_forums()) : bbp_the_forum();
                    bbp_get_template_part('loop', 'single-forum');
                endwhile;
                bbpress()->forum_query = clone $temp_query;
            }
            else /* Otherwise, we print the forums the normal way */ {

                bbp_get_template_part('loop', 'single-forum');
                $bbp_forums_noheader = 1; /* This prevents the header part to be printed again on next post in the loop */
            }
            ?>

        </li><!-- .bbp-body -->

    <?php
    /* Prints the footer only if :
      - it's a category
      - or if it's the last forum of a no-parent forum list
      - or if the next forum in the loop is a category */

    if (bbp_is_forum_category()
        OR ( bbpress()->forum_query->current_post + 1) == bbpress()->forum_query->post_count
        OR bbp_is_forum_category(bbpress()->forum_query->posts[bbpress()->forum_query->current_post + 1]->ID)) {
        ?>

            <li class="bbp-footer">

                <div class="tr">
                    <p class="td colspan4">&nbsp;</p>
                </div><!-- .tr -->

            </li><!-- .bbp-footer -->

        </ul><!-- .forums-directory -->

        <?php unset($bbp_forums_noheader); /* Needed if we have 2+ no-parent forums with at least 1 category between them */
    }
    ?>

<?php endwhile; }?>

<?php do_action('bbp_template_after_forums_loop'); ?>