| Not exactly Duolingo alternative, but: I'm currently building an an app for language learning by reading books. It takes an (your) ebook and inserts translations: —Arthur —dijo con tono cortante, ["Arthur," he said sharply.] y su voz sonó como el chasquido de una ratonera—, [and his voice sounded like the click of a mousetrap.] There is zero gamification, as it's not needed - you're motivated by the pleasure of reading. It won't help you to learn to speak (there is an option to read aloud a selected phrase though), but it will help you with vocabulary. I went with it from not being able to read even one page, to being able to understand 70% of a book (intermediate Spanish level) in about a month. ATM looking for beta users, completely free of charge. Pls leave a contact in a comment if you're interested |
https://github.com/joelparkerhenderson/ has the guide books. Topics include startups, UI/UX, programming, project management, etc.
Feel free to email me joel@joelparkerhenderson.com. I can give you access to the repos, if you wish to add your translations there too. You're on to a really great idea IMHO.