I’ve never so much as shot a gun, so no, never had an open carry.

Huh, I had no idea that was the case. How does what3words make money exactly? I assume ads but I block those everywhere I use a screen.

Are there any services that do roughly the same thing but are open source?

The what3words app is awesome and lets you share any 10-foot square on the planet and save them into lists.

It’s not on F-Droid, but I use BlipBlip for this exact thing. It’s an old app sadly, but still works on Android 14. There’s a ton of customization options which you might find useful.