[@strategeek Participant 11 years, 2 months ago]

FINAL CODE HERE.
FOR CHECK BOXES.
(Difference from the upper one: fixed issue with tags with more than 1 word)

function displayTagElements($selectedTags, /* $userRole, */ $task){
   $html= array();
$tags = get_categories(array('hide_empty' => 0, 'taxonomy' => 'topic-tag'));
$selectedTagsArray = explode(',', $selectedTags);
if($userRole != 'bbp_participant' || $task != 'edit') {
    $html[] = "";
    foreach($tags as $tag) {
        $selected = '';
        if (in_array($tag->name, $selectedTagsArray)) {
            $selected = 'checked';
        }
        $html[] = "<input type='checkbox' name='bbp_topic_tags[]'".$selected." value='". $tag->name ."'>". $tag->name ."&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;";
    }
} else {
    $html[] = $selectedTags;
}

return implode('', $html);