bbPress.org

Also in form-reply.php & form-topic.php template files (around line 68ish) you need to insert the following code. i would recommend setting up template overrides for this

<?php if ( bbp_allow_topic_tags() && current_user_can( 'assign_topic_tags' ) ) : ?>

        <?php do_action( 'bbp_theme_before_reply_form_tags' ); ?>
        <p>
            <label for="bbp_topic_tags"><?php _e( 'Tags:', 'bbpress' ); ?></label><br />
            <?php  echo displayTagElements(bbp_get_form_topic_tags(), bbp_get_user_role(get_current_user_id()), 'edit'); ?>
        </p>

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

<?php endif; ?>