The situation is a bit curious right now. We have a big Peterson-made online course and a book coming in autumn, so we can expect our current incomplete knowledge to become obsolete, so jumping into a massive project like Duolingo course seems to me an ill advised effort. And when the course and book do come out, there is another question: are we interested in making a competing (and free) course. I think not. There's probably still room for fan material, but keeping a respecting attitude will become more of an issue. At worst even legality might challenged. Languages are not terribly well copyrightable, but cut&pasting lessons from Peterson's work won't do and when you have one authorative learning source, doing things differently ends up easily just intentionally degradating material, which is an ugly road to take.
That being said, I will at least consult, if people get their mind on doing this thing. I'm not sure, if I'll be directly involved. I'm already doing badly enough with keeping the wiki current and developing.
