Validating in behavior (recapcha)

Could you please elaborate on these bits of glue code and logic?

I am currently trying to implement a v2-recaptcha in the plone 4.3.3 member self-registry and it turned out to be a major headache. How can i add anything to @@register oder @@register-confirm-email? When added with TAL in a customized view the recaptcha is working - but how can i add it to @@register?
All i found in forums were instructions about some python files, but i lack the basic knowledge of where to begin. Is there any way to achieve this in zope?

So far i tried with collective.recaptcha, collective.registrationcaptcha, plone.formwidget.recaptcha and collective.emailconfirmationregistration, but i can't find any view or option for @@register anywhere.

Edit: i opened a new thread for this question