Use following approach to get the translated text for a field from server script. This approach is applicable for any fields of type "Translated Text" or "Translated HTML".
Execute following server script code to get the translated text:
// get translated text
var trans_text = '';
var gr = new GlideRecord("<tablename>");
if (gr.get("sys_id","<sysid>")) trans_text = gr.getDisplayValue('<fieldname>');
In the above replace the placeholders with following:
<tablename> is the name of the table where the translated field exists.
<sysid> is the sys_id of the record
<fieldname> is name of the translated field.
The value in variable trans_text will be dependent on:
a) the current language selected for the user's current session.
b) if a corresponding record exists in the sys_translated_text table. If no translation record is found, the English version of the field's value will be returned.