You can use several different biblical terms lists, to choose your project terms list. So if you want Greek, go to the menu in BTL, choose select Biblical Terms List…, and then choose the list Major Biblical Terms. You can then click on the star to the extreme left of the line the term is on, and it will add that term to your Project BTL (Biblical Terms list). All of these terms have the original Greek or Hebrew.
The NT Key Biblical Terms list is chiefly useful for terms that have more than one sense (for example, grace), and that is all that I use that list for, when I need to track different senses of the Greek word.