Hi everyone! This is my first post to this forum. It looks like a lot of fun! 
I sure wish I would have discovered this forum when I first started studying Ancient Greek (about 5 years ago). I’ve previously been active on Quora and Reddit, where I slowly transitioned from mostly asking questions to mostly answering questions.
I recently discovered Duolingo, which I ignored for years because it didn’t offer Greek. I decided to try their Modern Greek course to test the platform, and I have to say that I’m quite impressed.
The platform has some nice algorithms and great corrective mechanisms in place, for users to provide feedback to the volunteer developers who can modify the courses on the back-end. So the courses improve themselves over time, which is really great.
Notably, the platform offers courses in languages like Esperanto, Kingon and High Valerian. But Latin is currently the only Classical language in the works. And this makes me somewhat frustrated that Ancient Greek is not being given an equal opportunity!
It seems like Duolingo requires about 10-or-so volunteers to develop a new course, with each volunteer contributing about 5-10% of the content. If you’d be interested in helping as a course developer, please apply on the Duolingo “Incubator” site. You’ll have to submit a writing sample in Ancient Greek (Attic, Koine or whatever floats your boat).
I’ve started a Facebook page (Ancient Greek for Duolingo) and Facebook Group (Ancient Greek for Duolingo Group) in order to help rally future volunteers and potential students. I think this will be the best platform for gauging the public interest in a measurable fashion. The Duolingo forums don’t seem adequate for this, IMO.
The trajectory of the course will probably be open to debate among the collaborators. But I would vote for the course to be based, ideally, in Attic Greek (using vocabulary & grammar from the Italian edition of Athenaze, for example). But, Koine and Homeric forms could be included - to cast a wider net and bridge the gap between various Greek enthusiasts. This seems to be quite manageable on the Duolingo platform.
I already have a ton of Ancient Greek resources in a Filemaker Pro database (glossaries, declension tables, conjugation tables) which I can easily export into delimited data format. I’d like to leverage this existing material for developing a Duolingo course.
I also have several Greek courses on my Memrise account, for anyone interested. I’ve been instructed not to post links here. But you can find the page by visiting Memrise(dot)com/user/Diachronix/. I have courses in Modern Greek and Ancient Greek, including verb drills and principal part drills. I also have the vocabulary from the English and Italian editions of Athenaze.
Thanks!