Oh, it's even better than that. If you look at the cloudemailapp source code, the client testimonials list from the mailgun source is there, just commented out:

Line 188:

  <!--<h2>
  Customers 
    <a href="customers/index.html" class="btn">case studies</a>
  </h2>

  <div class="paper customers">
    <div class="stage1">
      <img src="static/img/logos/yc.png" alt="YC" />
      <img src="static/img/logos/uservoice.png" alt="Uservoice" />
      <img src="static/img/logos/colourlovers.png" alt="Colorlovers" />
      <img src="static/img/logos/ft.png" alt="FT" />
      <img src="static/img/logos/everyblock.png" alt="everyblock" />
    </div>
  </div>-->

They also are using the exact same generated Optimizely JS file on line 9.

What's really shocking is this doesn't seem like just a copy of the site -- it's like a copy of the entire product, which is really amazing. I have to wonder if it even works...