Speaking as a total ignorant from a coding perspective. But I guess that wouldn't be the hard part, considering that most of Duolinguo is just boxes and text inputs. How difficult it is to create a database of competent linguists with an efficient training who can progressively enhance your understanding of languages?
it doesn’t live up to his expectations while being made by someone else on their free time. This mentality is rampant in opensource.
Is he going to contribute, not likely
is he going to donate so they can work on it, also no
is he going to vaguely ask others to make an app to compete with commercial companies, Oh yesss
Pretty much the gist I was trying to extract from the user or get some insights on.