I wrote a small program to help translate mods.
It is very simple to use: load the locale file for translation, load the translation (if there is one already), select the strings for translation in the list on the left, the source text and the translation below are displayed on the right.
If text was changed in new locale, you can load 2 source files (old and new) to see changes and translate changed strings.
Latest Version: 1.4.5
Note for Chinese users:
Some symbols can display incorrectly because of GB2312 charset used in Chinese Simplified locale.
The workaround is to use "Locale-Emulator" software for running FLE from it. See here.
Thanks to Mumu for investigation.