The Apache Software Foundation - 6.61MB (Open Source)
Apache HTTP Server is a Web server application that is developed and maintained by an open community of developers under the guise of The Apache Software Foundation.
The application is available for a wide variety of operating systems, including Unix, Linux, OS X and Microsoft Windows.
Apache supports a plethora of features, many of which are implemented as compiled modules that can extend the core functionality. These range from server-side programming language support to authentication schemes.
KEY FEATURES INCLUDE:
The source code is freely available so anybody can adapt the server for their specific needs. Also there is a huge public library of Apache add-ons.