The Kosher part isn't necessary. But I have used Sea Salt with the same results.
Which reminds me - why is called 'Sea' salt? All salt is a deposit from an ancient ocean, whether it is on a salt flat or in a mine 2000 feet underground. Ergo, all salt is sea salt.
And another question. Why is there an expiration date on a container of salt? It sat underground for 2.5 billion years with no problem, then all of a sudden because it's been mined and put in a box it's going to go bad sometime between now and the end of humanity as we know it? I think not.