[Plugin: WP-reCAPTCHA] reCAPTCHA only for registration page in WPMU?

Hi,

I want to use WP-reCAPTCHA for my WPMU install.
But I only want to use it for registrations only.

Any idea how to do this?
What lines would I have to remove in order to do this?

Thanks for reading!

[EDIT]
Okay ignore my stupidity!
I was thinking about the forced activation. If I use optional MU activation, I should be able to do what I need!