How to setup Recaptcha on pages cached by Varnish? On a site where a contact form is displayed at the bottom of each page, I implemented Varnish caching. To do so I had to deactivate Recaptcha to avoid 'no cache -must revalidate " headers. 

I tried other antispam solutions such as Honeypot or Botcha, but Honeypot is not efficient (at least with time limit  disabled), and Botcha also invalidates cache. I'd really prefer to go on with Recaptcha

I tried also Boost Captcha dev version : as per this related Varnish issue, it should be quite straightforward to make it work for Varnish. But this doesn't help, cache  is still invalidated.

Did anybody could make Recaptcha work with Varnish ?
CAPTCHA and reCAPTCHA modules are incompatible with page caching.