No , at this moment it cannot be used on user generated forms. We played around with it , trying to get it to work on them, but ended up manually creating the forms through a class , the recaptcha works perfectly then.
nice work! one tiny note: we favour the usage of FormField::createTag() in FormField->Field() because its easier to read and modify.
do you want me to set up your module as a component on open.silverstripe.com and add it to translate.silverstripe.com? as always, we're offering to host your module on our subversion-repo as well if you're keen :)
I based myself on the recaptchamodule, don't remember seeing createTag there, but I can change it in a next version some day.
The guys from mollom asked me to set up a little site for it http://mollom.silverstripe.be/ where I maintain the versions, but feel free to add it to translate and open. (although it might need some extra vars added to translate).
I'm also looking into adding Mollom as a whole (as a Validator extension) - which checks the content first and only adds a Captcha on 'unsure', but I'm running into some difficulties with Validator and Form - might open a topic for it later that describes my problem in detail.