The source code

    // Copyright 2007 Google Inc. All Rights Reserved.
    //
    // Sets up google.gears.*, which is *the only* supported way to access Gears.
    //
    // Circumvent this file at your own risk!
    //
    // In the future, Gears may automatically define google.gears.* without this
    // file. Gears may use these objects to transparently fix bugs and compatibility
    // issues. Applications that use the code below will continue to work seamlessly
    // when that happens.

    (function() {
      // We are already defined. Hooray!
      if (window.google && google.gears) {
        return;
      }

      var factory = null;

      // Firefox
      if (typeof GearsFactory != 'undefined') {
        factory = new GearsFactory();
      } else {
        // IE
        try {
          factory = new ActiveXObject('Gears.Factory');
        } catch (e) {
          // Safari
          if (navigator.mimeTypes["application/x-googlegears"]) {
            factory = document.createElement("object");
            factory.style.display = "none";
            factory.width = 0;
            factory.height = 0;
            factory.type = "application/x-googlegears";
            document.documentElement.appendChild(factory);
          }
        }
      }

      // *Do not* define any objects if Gears is not installed. This mimics the
      // behavior of Gears defining the objects in the future.
      if (!factory) {
        return;
      }

      // Now set up the objects, being careful not to overwrite anything.
      if (!window.google) {
        window.google = {};
      }

      if (!google.gears) {
        google.gears = {factory: factory};
      }
    })();

    if (!window.google || !google.gears) {
        location.href = "http://gears.google.com/?action=install&message=Google%20Gears%20is%20required%20for%20this%20application" +
                    "&return="+window.location.href;
    }