vine.js

// ==UserScript==
// @name         Vine download link
// @namespace    http://www.robert-deluca.com
// @version      0.1
// @description  Download a vine video
// @author       Robert DeLuca
// @match        https://vine.co/*
// @grant        none
// @require  https://gist.github.com/raw/2625891/waitForKeyElements.js
// ==/UserScript==

function addVideoURLToSingleVideo() {
  var s = $('.main .vine-video-container video').attr('poster');

  var videoURL = s.substring(0, s.indexOf('.jpg'));
  var constructedLink = '<a href="' + videoURL + '" class="custom-vine-dl-link" style="display: block; margin-top: 10px"">Download Video</a>';
  $('.post-social-metrics').append(constructedLink);
}

waitForKeyElements (".main", addVideoURLToSingleVideo);

function addVideoURLToMulti() {
  if($('.post').hasClass('ember-view')) {

    var s = $('.vine-video-container video').attr('poster');
    var videoURL = s.substring(0, s.indexOf('.jpg'));

    var postActionsBtn = '<a href="' + videoURL + '"><button class="ember-view action clear share custom-vine-dl-link"><span style="transform: rotate(180deg);" class="icon-share_stroked"></span><span class="icon-share_stroked"></span><span class="caption">Download Video</span></button></a>'

    $('.post-actions').append(postActionsBtn);
    $('.post').removeClass('ember-view');
  }
}

waitForKeyElements (".post", addVideoURLToMulti);