What is the incentive for unpaid volunteers to add new languages to Duolingo?
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This is actually a very good question. We all certainly hope that people will want to add languages to duolingo , but it is going to be very insightful to see how that actually works. Until now I have basically just assumed it will work out, and though I have no doubt it will, I think that it will be a pretty large paradigm shift for duolingo. The whole thing has basically been handed out on a plate so far.
I would like to add my native language so my parents could learn English through this awesome and free website.
I imagine personal reasons some people like to try to teach people their native language there are also other people like esperantists who like to promote their auxiliary language because they believe in it etc.