form button redirecting to .inc module file
You redirect to a URL, you can't redirect to a PHP include file it's not possible. 

The function you give as the #submit key is run on form submission, it's not used to build up the next page request or anything like that.

Your code should look more like this:

$form['button']['addnew_form'] = array(
  '#type' =&gt; 'submit',
  '#value' =&gt; 'new form',
  '#submit' =&gt; array('MYMODULE_form_submit'),
);


Then you'll need a submit handler to match that:

function MYMODULE_form_submit($form, &amp;$form_state) {
  // Redirect to the appropriate URL.
  $form_state['redirect'] = 'myform/forms/newform';
}


You can add a second submit handler for your second button, with a different function name, and that redirects to a new menu item that you need to define which contains the second form.