find the following line near the bottom of the page:
var Date_of_Death_Spry = new Spry.Widget.ValidationTextField("Date_of_Death_Spry", "date", { format:'mm/dd/yyyy' , validateOn:["blur"]});
and change it to:
var Date_of_Death_Spry = new Spry.Widget.ValidationTextField("Date_of_Death_Spry", "date", { format:'mm/dd/yyyy' , validateOn:["blur"], isRequired:false});