They said here that they will upgrade when 0.18.1 releases. The reasoning was that 0.18 got rushed out the door and dropped captcha support when their APIs changed. It will be added back in in 0.18.1.
If you dont mind using Jerboa on an unsupported server (meaning don't complain when everything isn't perfect, dont be calling out bugs or reporting unpredictable app behavior, etc.), you can upgrade now. Just make sure you're logged into Jerboa, then hit up their github and install the latest release. Then when you open the app and it alerts you to the fact that the previous server version is not supported, click "ok" and carry on. The trick is to make sure youre logged into Jerboa when you do it. Your mileage may vary, proceed at your own risk, etc.