FreeCAPTCHA is a new CAPTCHA system for privacy-focused websites. No JS, minimal dependencies, all on-premise (no 3rd party APIs required).

Here's a minimalistic implementation, to show you what it looks like:

Let's try selecting an incorrect option:

And we submit, to see what happens:

Okay, what if select the correct image?

And smash that submit button to see where it goes!

Viola! Although the concept works, it's mostly just that, a proof of concept. The code needs to be modularized into a library that can be loaded into a little iframe for easy integration