This code for communicating reCaptcha API is taken from mrkshrt (Mark), at reCAPTCHA google-groups (10.2007).
There is a demo from Shaun3180 adding form, mailing etc. into Mark's code there,
(and, as a local copy here).
Mark's base functions use theme : 'white', while Shaun preferred 'clean'.

Now it's time for a quick and dirty test:

ajax call--