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: