The official Google Translate API is available for businesses only but you can use Google Apps Script to create your own Google Language Translation API without having to pay the enterprise license fee.

The text can be translated from one language to another using the LanguageApp service or, if you run out of quota, you can make a call to the secret translate.googleapis.com API that is internally used by the Google Translate extension for Chrome and requires no authentication.

You can publish the Google script and deploy it as a web app with parameters for source and target languages and the text query. You can specify any ISO language pair or say “auto” and the Google Translation API will auto detect the language of the source text.

/* Written by Amit Agarwal */
/* web: ctrlq.org          */

function doGet(e) {
  var sourceText = "";
  if (e.parameter.q) {
    sourceText = e.parameter.q;
  }

  var sourceLang = "auto";
  if (e.parameter.source) {
    sourceLang = e.parameter.source;
  }

  var targetLang = "ja";
  if (e.parameter.target) {
    targetLang = e.parameter.target;
  }

  /* Option 1 */

  var translatedText = LanguageApp.translate(sourceText, sourceLang, targetLang);

  /* Option 2 */

  var url =
    "https://translate.googleapis.com/translate_a/single?client=gtx&sl=" +
    sourceLang +
    "&tl=" +
    targetLang +
    "&dt=t&q=" +
    encodeURI(sourceText);

  var result = JSON.parse(UrlFetchApp.fetch(url).getContentText());

  translatedText = result[0][0][0];

  var json = {
    sourceText: sourceText,
    translatedText: translatedText,
  };

  // set JSONP callback
  var callback = "callback";
  if (e.parameter.callback) {
    callback = e.parameter.callback;
  }

  // return JSONP
  return ContentService.createTextOutput(callback + "(" + JSON.stringify(json) + ")").setMimeType(
    ContentService.MimeType.JAVASCRIPT
  );
}