Open Access Point Issues

Sorry, this looks like a bug. It seems like you can just work around it by specifying a password (which will then get ignored):

wifi.startAP('EspruinoAP', { password: '0123456789', authMode: 'open' }, function(err) {
  if (err) throw err;
  console.log("Connected!");
});

However I've just made some fixes so the next version of the Espruino WiFi firmware won't have this issue.