reCAPTCHA4net is a fork of Recaptcha for .NET project. It allows to easily integrate Google reCAPTCHA service into ASP.NET web application. Both Web Forms or ASP.NET MVC are supported. While reCAPTCHA4net has full backward compatibility with the Recaptcha for .NET assemblies, it supports updated reCAPTCHA API, which provides the No CAPTCHA experience.
Currently reCAPTCHA4net is hosted on CodePlex and mirrored on GitHub. It allows you to make a fork in any place you want. You can find the latest news about the project at https://recaptcha4net.codeplex.com/.