Yeah, it's open source and updated constantly. As you say it's free though and gets you "in the ball park" 🙂
Just got the new update for 27th of Aug and it fixed most of the issues I had with wrong power costs ect. There still is some primaris stuff mixed in, but that's easy enough to ignore.
"Your vision will become clear only when you can look into your own heart. Who looks outside, dreams; who looks inside, awakes. " - Carl Jung