To see why the Internet and open source are a good fit for each other, we first have to look at the origins of the Internet as we know it today. Before the mainstream explosion of the web in the 1990s, the Internet was still very much the domain of universities, colleges, laboratories, and governments. It was still mainly under research, which gives us our first clue because the scientific community has long valued the open cooperation of its members. Initially, all software was open source simply because nobody had the idea of charging money for it.
Sir Tim Berners-Lee, widely recognized as the father of the World Wide Web (before this, there was just “internet”), created the first web server while working at CERN running his HTTP protocol. His system was NeXTStep – a derivative of Unix and the BSD operating system. The web browser which first popularized the World Wide Web was Mosaic by NCSA, built on a Unix system and released as open source.
So there was open source and Unix at the very beginning. Both of the major web browsers in use today, Internet Explorer and Mozilla Firefox can trace their roots directly back to the Mosaic web browser. As for the World Wide Web, one need only consider that to this day, directory paths for website URLs follow the forward-slash (/) convention of Unix file systems rather than the back-slash () of DOS systems.
In addition, even Apple as we know it today owes some of its existence to Free and Open Source software since the OS X operating system has BSD, another open-source Unix-based system, running under the hood. So we have Linux, BSD, OS X, and then Solaris, a Unix-like system in open source form under Open Solaris. After that, the remaining stragglers bringing up the rear are all open source, Unix-related, or both today. So, Microsoft is the exception rather than the rule, though even Windows is built on top of DOS, which itself started as a copy of CP/M, which – you guessed it! It descended from Unix.
By nature, the Internet and the World Wide Web are only helpful if they are as free of constraint as possible and allow every system from everywhere to cooperate under a united standard. And so the path of least resistance has been open-source software, usually free. The default system over the history of computers has been Unix and its derivatives, and the most popular Unix version today is Linux.
No one could even imagine it as being otherwise. This truth hides behind the current desktop dominance of a closed-source proprietary system – it is the exception, not the rule.