The developers have announced on their website that a new version of Ivory is going to be released. There is nothing there except a static page and a form to register your email to receive news and updates about the development of Ivory. I suggest you enter your email to register for these updates and when a new version will be released you'll be notified along with High Sierra 10.3.1/3 support.
Access their website to enter the email address.
Note: Confirmation might be necessary after the form is submitted.