The added value here seems to be the curated, per-language word list. You'd have to be careful with homophones, they say that they use simpler, more common word

The added value here seems to be the curated, per-language word list. You'd have to be careful with homophones, they say that they use simpler, more common words for populated locations (and locations where the target language is more used) etc... After playing a bit with their interface I can't really tell if they're successful but it does seem like it would be relatively complicated to come up with such a word list in many languages. That being said, it could probably be crowdsourced.