You'd need some server side code to handle the form posts and this is not possible in static websites. Hence the app. This can even be done by using 'Google for

You'd need some server side code to handle the form posts and this is not possible in static websites. Hence the app. This can even be done by using 'Google forms' and 'Wufoo'. However, they give you code which contains iframes. SimpleForm doesn't restrict you in any way, you just need to setup the form's action and method and you are set :)