What @romanovcode means is : Of course it's free. Someone would have to be certifiably insane to pay you for a pair of numbers. We know it, and you know it. So emphasizing that part as some sort of statement of distinction makes you look hilarious.
Oh I get it.
I'll be honest. 'Free' stands there to attract more people.
By the way. We have raised a few hundreds of $ in donations.
Thus there are lots of 'insane' people ;)
I'm actually really glad that you're getting donations. Design visuals like yours can be really handy. It's not something that you could readily monetize, so it's nice to hear that people are tipping if they find it helpful. (tbh I'd put ads on the page)
Also, drop that exceedingly long loading screen if you can. Nobody likes to wait that long.