Sorry I'm not quite sure which bit of the code you mean - I think you mean this bit.
Code:
$templater = vB_Template::create('edittask');
$templater->register_page_templates();
$templater->register('navbar', $navbar);
$templater->register('pagetitle', $pagetitle);
$templater->register('type_tasks_options', $type_tasks_options);
$templater->register('task_user_options', $task_user_options);
$templater->register('taskmanagerversion', $taskmanagerversion);
$templater->register('editorid', $editorid);
$templater->register('messagearea', $messagearea);
$templater->register('edittask_name', $edittask_name);
$templater->register('itemid', $itemid);
$templater->register('edittask_id', $edittask_id);
$templater->register('edittask_name', $edittask_name);
$templater->register('edittask_desc', $edittask_desc);
$templater->register('edittask_assigned', $edittask_assigned);
$templater->register('edittask_duedate', $edittask_duedate);
print_output($templater->render());
The message text variable is "$edittask_desc"