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Android(s GOOG) users with aspirations of learning another language have a new app to check out. About six months after rolling out an iOS(s AAPL) app, Duolingo on Wednesday launched its Android app.

Created by Recaptcha founder and Carnegie Mellon professor Luis von Ahn, Duolingo helps people learn languages while translating real-world content from the web.

Built from the bottom up for the new platform, von Ahn said, the Android app could help the company as much as double its user numbers. At the moment, the app has 3 million registered users, half of which are on mobile and 1 million of which are active. Already, it has broad appeal among non-U.S. users – about 70 percent are not from the U.S. – but considering the number of non-U.S. Android fans, von Ahn said that number could rise quickly.

Like the website, the Android app offers skill-based, game-like lessons, but they’re optimized for a smaller screen and shorter chunks of available time. They’re easier to complete while you’re waiting for the bus or in line at the store, and they require less typing.

In the last month and a half, the iOS app added the ability to download lessons for offline use (great for subway commutes) and a feature for recording yourself speaking the language (so the app can assess your pronunciation). The Android app doesn’t yet include those features, but von Ahn said they should be added later this summer.

First revenue-generating deal with publisher

Until now, the service has offered web and mobile users theme-based, mastery-level-appropriate lessons, as well as opportunities to translate real-world web content. But von Ahn said the company just signed its first partnership with a U.S. publisher, meaning that users will begin to translate actual news articles from English to Spanish.

He declined to share the name of the publisher, but said the deal marks the startup’s first revenue-generating partnership and points the way to how the company intends to make money. At any given time on the service, he said, about 80 percent of the users are completing lessons, while 20 percent are translating content. But even though a smaller percentage is translating, he added, users can translate a 500- to 600-word article in about an hour.

Now that the company is beginning to make money from the translations, von Ahn said it may experiment with new ways of incorporating translation opportunities into the lessons and other parts of the experience.

“We haven’t had a huge incentive to push the translations because they haven’t been generating revenue,” von Ahn said. But “we’ll never force you. What I hope is that users like them – and they actually do.”

In the past few months, interest in language-learning startups seems to have picked up. Last month, Rosetta Stone, a giant in the space, acquired language-learning community LiveMocha. And in April, Berlin-based language learning service Babbel acquired PlaySay, a small Silicon Valley language-learning app, and raised $10 million.

Despite increasing competition, Duolingo’s traction seems to be growing at a healthy clip. Since the startup raised a $15 million Series B round in September, its number of active users has quadrupled. A study earlier this year found that it takes a Duolingo user 34 hours to learn the equivalent of one semester of college-level Spanish, while it takes a Rosetta Stone user 60 hours to learn the same amount of content.