votes only in "updown" widget for teasers

The updown theme included in the official download will not work like this, but its fairly easy to make duplicate the updown theme, rename it and slightly mod its design as per your needs.

+1
IMHO this could be a frequent feature.

I was trying to make a conditional theming, but the actual variables passed to widget.tpl.php does not include such a variable.

A get_defined_vars() gave me:

array
  'template_file' => string 'sites/all/modules/vote_up_down/widgets/updown/widget.tpl.php' (length=60)
  'variables' => 
    array
      'cid' => string '38' (length=2)
      'type' => string 'node' (length=4)
      'widget_theme' => string 'updown' (length=6)
      'tag' => string 'vote' (length=4)
      'class_up' => string 'up-inactive' (length=11)
      'class_down' => string 'down-active' (length=11)
      'link_up' => string '/vote/node/38/1/vote/22f85aca08ec337974cdcc65e00305f3' (length=53)
      'link_down' => string '/vote/node/38/-1/vote/4093c96b677a958f7e881abbafaf67c9' (length=54)
      'unsigned_points' => int -1
      'points' => int -1
      'class' => string 'negative' (length=8)
      'vote_label' => string 'votes' (length=5)
  'cid' => string '38' (length=2)
  'type' => string 'node' (length=4)
  'widget_theme' => string 'updown' (length=6)
  'tag' => string 'vote' (length=4)
  'class_up' => string 'up-inactive' (length=11)
  'class_down' => string 'down-active' (length=11)
  'link_up' => string '/vote/node/38/1/vote/22f85aca08ec337974cdcc65e00305f3' (length=53)
  'link_down' => string '/vote/node/38/-1/vote/4093c96b677a958f7e881abbafaf67c9' (length=54)
  'unsigned_points' => int -1
  'points' => int -1
  'class' => string 'negative' (length=8)
  'vote_label' => string 'votes' (length=5)

So, where should I add a $is_teaservariable ?

this is fixed by #670146: display voting widget even if user doesn't have permission to vote?

now you have a $readonly variable on widget.tpl.php's