"Are you talking about something like Google Translate?"
"yes like Google Translate"
You are very, very unlikely to find any worthwhile source code for this: it is complex, expensive-to-produce and valuable Intellectual Property which is closely guarded by it's creator.
Why not use Google Translate itself? Until recently, they provided an API which allowed you to use it, but unfortunately it was badly abused and will be shut off compleletly in December. They do still provide
Elements[
^] which may be able to help you.