Prototype plugin for dynamically expanding textarea

Does anyone know of a good plugin for prototype which allows textareas to automatically expand / contract based on how much text there is in them (e.g. a line is added the area gets bigger, a line is removed it gets smaller)?

I need one thats free to use (e.g. some form of GPL type license).

From stackoverflow

• It's not a plugin, but it's not long: http://www.codelibary.com/JavaScript/Auto%20textarea%20resize.html.

  EDIT: found this SO thread

  ddaa : Your codelibrary link appears broken.

• This uses Prototype:

  <textarea id='t1' cols="40" rows="7" style='overflow:hidden;font-size:14px;font-family:"Times New Roman", Times, serif'></textarea>
  <script type="text/javascript">
  function activateResize(element) {
      Event.observe(element, 'keyup', function() {
        updateSize(element)
      });
      updateSize(element)
  }
  
  function updateSize(element) {
     //if scrollbars appear, make it bigger, unless it's bigger then the user's browser area.
      if(Element.getHeight(element)<$(element).scrollHeight&&Element.getHeight(element)<document.viewport.getHeight()) {
       $(element).style.height = $(element).getHeight()+15+'px'
       if(Element.getHeight(element)<$(element).scrollHeight) {
        window.setTimeout("updateSize('"+element+"')",5)
       }  
      }
  }
  
  activateResize('t1')
  </script>
  

  : I based the code I used on this, thanks.