A captcha is a tool that will allows you to stop spam users from your website, but spam user it mean the users create by bots.
The component will add a captcha on signup page.
For the captcha, it would be good to give to possibility to refresh the captcha if it is unreadable (to have another one) or simply to have another captcha if it is wrong typed !
delete and install it again. on my site works very fine (y)