Who developed Recaptcha?
ReCAPTCHA
The reCAPTCHA tests are displayed from the central site of the reCAPTCHA project, which supplies the words to be deciphered.  This is done through a JavaScript API with the server making a callback to reCAPTCHA after the request has been submitted.  The reCAPTCHA project provides libraries for various programming languages and applications to make this process easier.  reCAPTCHA is a free service (that is, the CAPTCHA images are provided to websites free of charge, in return for assistance with the decipherment),[26] but the reCAPTCHA software itself is not open-source.[27]