You don't need a private client key for just encryption, the public key of the recipient is sufficient.

For signing, you'd need a pub/priv keypair, but this is not implemented here.

   $.get("/static/pgpkey", function (key) { 
      // store key
      // hook to submit button click event & encrypt before submit
   });

for the pgp encrypting he's using http://openpgpjs.org/