[BirdOPrey5]

No it won't work once per thread because Pinterest is designed for sharing media and that is usually specific to posts.

If you wanted to show it only on the first post though you could edit the "Pin button in Posts" plugin and find the code:

if ($vbulletin->options['bop5pin_en'] AND 
    !is_member_of($vbulletin->userinfo, explode(",", $vbulletin->options['bop5pin_groups'])) AND
    !in_array($thread['forumid'], explode(",", $vbulletin->options['bop5pin_forums']))  )

and change it to:

if ($vbulletin->options['bop5pin_en'] AND $post['postcount'] == 1 AND
    !is_member_of($vbulletin->userinfo, explode(",", $vbulletin->options['bop5pin_groups'])) AND
    !in_array($thread['forumid'], explode(",", $vbulletin->options['bop5pin_forums']))  )