If you want to remove the requirement yourself, you need to edit zc_install/includes/templates/database_default.php

around line 130 you should see this javascript

Code:
$().ready(function() {
  $("#db_setup").validate({
    submitHandler: function(form) {
      ajaxTestDBConnection(form);
    },
    rules: {
      db_host: "required",
      db_user: "required",
      db_password: "required",
      db_name: "required",
      sql_cache_dir: {
        required: function(element) {
          return $("#sql_cache_method").val() == 'file';
        }
      }  
    },
    messages: {
    }
  }); 
});
and you need to remove the line

Code:
      db_password: "required",