Language Instruction for Duolingo completely free - now and forever - without advertising and miscellaneous charges. How is that possible? Helping to translate the actual documents in the learning process, you bring income Duolingo.
Here's how it works. Those who need to translate the page loads it on Duolingo. Then this text is available on Duolingo students who translate it, thus training the language they are studying. When the text is fully translated, Duolingo returns to its author, who, in turn, pays for transfer depending on the type of the loaded document.