Outdated but useful

This plugin doesn’t seem to be maintained anymore though I could get it working. In order to initially set it up, I used the URL https://www.google.com/recaptcha/ rather than the one to which it directed me [it was broken]. Then, I clicked Get reCAPTCHA. You’ll need to login and there you can access the site key (public) and secret key (private).

Lastly, the label formatting in IE looked terrible so I commented it out of the php code.
$html .= ‘<label>CAPTCHA code</label>’;

Once it started working though, it was very helpful. The only similar plugins I found were paid.