It does not use reCAPTCHA. It is unrelated to any other CAPTCHA system. It does a simple CAPTCHA that you can modify to match your site. It does not use a lexicon, so it is a random string and not a series of words and it's distortion is based on random rotation and position of letters and noise levels that can be adjusted.
It should be relatively easy to add to your page with form toolkit, but really simplicity is more relative to the person than it is to the task, but you can get answers here if you have questions or issues along the way.