The problem with recaptcha alternatives is that they either are insecure or require time and money to continue to be ahead of bots.
All of the "interactive stand-alone approaches" from that page can be beaten with run-of-the-mill OCR (other than perhaps the 3d challenge) and with almost any mobile phone speech recognition engine (and, if the attacker has the money, can send it off to Google's cloud speech-to-text).
All of the non-interactive approaches from the page require this constant tuning and upkeep to make sure bots aren't able to sign up/abuse systems. There's also not \that\ secure if your website is targeted and scripts are made specifically to avoid your anti-abuse methods.
All of the "interactive stand-alone approaches" from that page can be beaten with run-of-the-mill OCR (other than perhaps the 3d challenge) and with almost any mobile phone speech recognition engine (and, if the attacker has the money, can send it off to Google's cloud speech-to-text).
All of the non-interactive approaches from the page require this constant tuning and upkeep to make sure bots aren't able to sign up/abuse systems. There's also not \that\ secure if your website is targeted and scripts are made specifically to avoid your anti-abuse methods.