With the new reCAPTCHA, most of the time end users don’t need to solve a visual captcha: all they need to do is to click the checkbox. That’s why this new reCAPTCHA is presented to all users, not just to non-logged in users.
I just released 4.1, which will copy the old public key to site_key and private key to secret. Note that with new reCAPTCHA global key is no longer supported. So if your site is using global key, you’ll have to go to https://www.google.com/recaptcha/admin#create to get a new key.
