Contributions are accepted from anyone. The core team integrates additions into an upgrade and posts it for free, source code and all. But Apache's main draw isn't that it's free. Apache is easy to customize thanks to modular architecture. The most commonly used modules ship with the Apache source code.
Users can find additional modules on the Web or build their own.
The server is used by many of the world's biggest, most demanding Web sites. Because Apache is developed by Web fanatics, it is always one of the first Web servers to support new standards and new technologies. Apache isn't without its drawbacks. For one thing, Apache runs on Unix but not on NT, though an NT version is in the works. Fortunately, there are dozens of books and newsgroups devoted entirely to Apache, so technical answers are usually easy to find.