Is it possible to add a link to download a file that can only be downloaded by sharing it on Facebook?

UPDATE

According to a Facebook new policy, this act is not allowed. Use it at your own risk. I hold no responsibilities for using this.

Yes, using the JavaScript SDK, it provides a response (it doesn’t anymore)
We will create an if statement to see if the response has a post_id if yes show the download link else do something else (alert the user, maybe?)

DEMO (API 2.0) (not working; revision required)

DEMO (API 2.7) working Rev#63

HTML

<div class="container">
    
    <div>
       <p>This file is locked, to unlock and download it, share it</p>
       <p class="hidden">Thanks for sharing, the file is unlocked and ready for download</p>
       <p class="hidden">In order to download this file, you need to share it</p>
    </div>

    <a class="fsl fsl-facebook" href="#" id="facebook-share">
       <span class="fa-facebook fa-icons fa-lg"></span>
       <span class="sc-label">Share on Facebook</span>
    </a>

    <a class="fsl content-download" href="#" id="download-file">
       <span class="fa-download fa-icons fa-lg"></span>
       <span class="sc-label">Download File</span>
    </a>
    
</div>

JavaScript (jQuery)

$('#ShareToDownload').on('click', function(e) {
            e.preventDefault();
            FB.ui({
                  display: 'popup',
                  method:  'share',
                  href:    location.href,
                  },
                  /** our callback **/
                  function(response) {
                          if (response && response.post_id) {
                          /** the user shared the content on their Facebook, go ahead and continue to download **/
                          $('#ShareToDownload').fadeOut(function(){ $('#downloadSection').fadeIn() });    
                          } else {
                          /** the cancelled the share process, do something, for example **/
                          alert('Please share this page to download this file'):
                  }
            });     
}); 

UPDATE

With the release of API version 2.0 the Feed dialog was deprecated and replaced with the new modern Share Dialog so the above code uses the new Share Dialog