Title: Google&#x27;s reCAPTCHA is everywhere, they seem to have the monopoly of checking if the user&#x27;s not a robot.<p>CAPTCHA systems are essentials to the web, and it seems important to me to have a (good) FOSS alternative, but I can&#x27;t find any.<p>Are all CAPTCHA closed-source to make it harder for attackers? Am I missing something?
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