Change required status of checkboxes
By default, Validation Checkbox widgets require the user to make at least one selection before submitting the form. You can, however, make selections optional for the user.
To change the required status of a checkbox, add
the isRequired property to the constructor and
set its value to false, as follows:
<script type="text/javascript">
var cb1 = new Spry.Widget.ValidationCheckbox("checkboxwidget1", {isRequired:false});
</script>