I think reCaptcha is very terrible. For HTML forms, a simple question could be used (change them sufficiently often when spam is received), or you may require t

I think reCaptcha is very terrible. For HTML forms, a simple question could be used (change them sufficiently often when spam is received), or you may require the user to edit the URL manually in order to access something, based on the client IP address perhaps (which would be displayed). I also invented a protocol-independent CAPTCHA, which is also text-based, and uses SASL. You should allow the user to implement the code themself if they want to do rather than requiring that they use your code.