To initialize GDE with data downloaded from a server, first download the file, and then pass the file contents to GDE.

IEnumerator InitGDE () {
  WWW payload = new WWW("http://example.com/gde_data.txt");
  yield return payload;

  if (!GDEDataManager.InitFromText(payload.text)) {
    Debug.LogError("Error initializing!");
  }
}

If your data was encrypted with GDE decrypt your data first:

IEnumerator InitGDE () {
  WWW payload = new WWW("http://example.com/gde_data_enc.bytes");
  yield return payload;
  
  string data = GDEDataManager.DecryptGDEData(payload.bytes);
  if (!GDEDataManager.InitFromText(data)) {
    Debug.LogError("Error initializing!");
  }
}