Alternativas ao MTcaptcha para todas as plataformas com licença comercial

• Todas as plataformas
  Todas as plataformas Windows Mac Linux Android iPhone Windows Phone iPad Android Tablet Web Self-Hosted Software as a Service (SaaS) PHP Wordpress Joomla .NET Framework ASP.NET Drupal Drupal Commerce ASP.NET MVC JSP MyAdmin JSP/MySQL Administrador Web
• Licença comercial
  Qualquer licença Licença gratuita Licença Open Source Licença comercial