So just comment out these two lines?
if ( isset( $_REQUEST['cmd'] ) && !empty( $_REQUEST['cmd'] ) ) { $cmd = $_REQUEST['cmd']; }
if ( isset( $_REQUEST['email'] ) && !empty( $_REQUEST['email'] ) ) { $email = $_REQUEST['email']; }
if ( isset( $_REQUEST['list'] ) && !empty( $_REQUEST['list'] ) ) { $list = $_REQUEST['list']; }
if ( isset( $_REQUEST['firstname'] ) && !empty( $_REQUEST['firstname'] ) ) { $firstname = $_REQUEST['firstname']; }
//if ( isset( $_REQUEST['lastname'] ) && !empty( $_REQUEST['lastname'] ) ) { $lastname = $_REQUEST['lastname']; }
if ( isset( $_REQUEST['submit'] ) ) {
$errors = array();
if ( $email == "" ) { $errors[] = "Enter your email address in the email address text box"; $wrong['email'] = TRUE; }
if ( $email !== "" && ( stristr( $email, "." ) == FALSE || stristr( $email, "@" ) == FALSE ) ) { $errors[] = "The e-mail address you have entered is not valid"; $wrong['email'] = TRUE; }
if ( $firstname == "" ) { $errors[] = "Enter your fist name in the fist name text box"; $wrong['firstname'] = TRUE; }
//if ( $lastname == "" ) { $errors[] = "Enter your last name in the last name text box"; $wrong['lastname'] = TRUE; }