Here's how to use the plugin.
1. Copy the reCaptcha folder under plugins directory.
2. Choose reCaptcha as the blog's captcha provider.
3. Edit Comment Form template, so it renders MTCaptchaFields unconditionally.  In practice, this means replacing these lines
    <MTIfNonEmpty tag="MTCaptchaFields">
    <MTIfCommentsAccepted><MTIfRegistrationAllowed><MTElse><$MTCaptchaFields$></MTIfRegistrationAllowed></MTIfCommentsAccepted>
    <div id="comments-open-captcha">
    </div>
    </MTIfNonEmpty>
to these lines:
    <MTIfNonEmpty tag="MTCaptchaFields">
    <div id="comments-open-captcha">
    <$MTCaptchaFields$>
    </div>
    </MTIfNonEmpty>
4. Edit Javascipt index template, to remove these lines of code which calls delayShowCaptcha:
    <MTIfNonEmpty tag="MTCaptchaFields">
    captcha_timer = setInterval('delayShowCaptcha()', 1000);
    </MTIfNonEmpty>
5. Rebuild index and individual entry archive.

