If you want to require customers to fill out a captcha field when they're signing up, first you'll need to configure captcha on your site and then all you have to do is include the following SmartTag in your checkout form:
[MM_Form_Field type='input' name='captcha' style='clean']
In order for this to work correctly make sure that you place the SmartTag between the
[MM_Form type='checkout'] and
[/MM_Form] SmartTags. After this SmartTag has been included in the checkout form MemberMouse will require that this field be filled out and match the captcha image before allowing the form to be submitted.
IMPORTANT: The MemberMouse Captcha SmartTag must be added to the Core Checkout Page in order to ensure the captcha fields work across all checkout forms on your site. If the SmartTag is not present on the Core Checkout Page, you will see an "Invalid Captcha" error on form submission.
Style the Captcha Form (MM 2.2.3 or lower)
This is only applicable to reCaptcha v1 which is included in MM 2.2.3 or lower.
style attribute indicates what the captcha form should look like and can be set to the following values: