The other side of the business comes in when students are asked to practice by translating single sentences from one language to another. Those sentences are currently taken from sites von Ahn thinks should be translated anyway, such as English Wikipedia articles without equivalents in Spanish.
Multiple students translate the same sentence; software compares those results to settle on a final translation. After many sentences are put through this process, they are combined to create a translation of an entire document. The results, says [co-founder Luis] von Ahn, are better than an automated translation but typically just short of professional quality.
The web translation service is currently free but, as Technology Review reports, the company will begin charging less than the five to 20 cents per word that a professional translator might charge, starting next year.