The reason the Register form is working is because it is a BuddyPress Register form, not a standard WordPress Register form. JTC only includes a BuddyPress Register form and a BuddyPress Sidebar Login form because BuddyPress uses the standard WordPress Login form for logins as well as having a Sidebar Login form if you use that feature. The Modal Login form has been customized and does not appear to be using the BuddyPress Sidebar Login form hook > add_action( 'bp_sidebar_login_form', 'bps_captcha_buddypress_sidebar_form_field' );. The Modal Login form is also not using the standard WordPress Login form hook directly in the form code > add_action( 'login_form', 'bps_captcha_login_form_field' );. Looking at the Modal Login form code they are sending a POST Request to the standard WordPress Login form, but unfortunately the Modal Login form itself does not have any hooks that BPS recognizes. You really only need to protect the Register form from spambots because if the spambots cannot auto-register spam accounts then they will not be able to auto-post spam posts.
.
