Think of it as a map of the rapidly changing world of computer software.

On Wednesday, Github published a graph tracking the popularity of various programming languages on its eponymous internet service, a tool that lets anyone store, edit, and collaborate on software code. In recent years, Github.com has become the primary means of housing open source software—code that's freely available to the world at large; an increasing number of businesses are using the service for private code, as well. A look at how the languages that predominate on Github have changed over time is a look at how the software game is evolving.

Open source is now mainstream. And the mainstream is now open source.

In particular, the graph reveals just how much open source has grown in recent years. It shows that even technologies that grew up in the years before the recent open source boom are thriving in this new world order—that open source has spread well beyond the tools and the companies typically associated with the movement. Providing a quicker, cheaper, and more comprehensive way of building software, open source is now mainstream. And the mainstream is now open source.

"The previous generation of developers grew up in a world where there was a battle between closed source and open source," says Github's Ben Balter, who helped compile the graphic. "Today, that's no longer true."

Java Everywhere

Case in point: the Java programming language. A decade ago, Java was a language primarily used behind closed doors, something that big banks and other "enterprise" companies used to build all sorts of very geeky, very private stuff. But as GitHub's data shows, it's now at the forefront of languages used to build open source software.

Among new projects started on GitHub, Java is now the second-most popular programming language, up from seventh place in 2008; according to Balter, the increase is driven not by private code repositories but by public (open source) repos. Among private Github repos, he says, Java ranks seventh.

It's now at the forefront of languages used to build open source software.

Why the shift? Java is so well suited to building massive internet services along the lines of Google, Twitter, LinkedIn, Tumblr, and Square, and the economics of the software business dictate that such services run on open source. As Balter also points out, Java's rise is also a result of Google making it the primary language for building apps on Android phones and tablets.

The graph also shows a recent uptick for C#. C# is basically Microsoft's version of Java; in years past, it was even more of a closed-source kind of thing. After all, it was overseen by Microsoft, a company that traditionally kept open source at bay. But as the influence of open source has grown, Microsoft has embraced the movement. It has even open sourced many of the tools used to build and run applications in C#.

Another language on the rise among Githubbers? Swift, Apple's language for building apps on the iPhone, iPad, and the Mac (the language doesn't show up in the graph, but in the raw data GitHub sent to WIRED, it now ranks art number 18 on the list). The reasons for this are different. Swift is on the rise because it's brand new and it's designed for the world's most popular smartphone. But its presence is another nod to growing importance of open source.

Unlike with its previous operating system, you see, Apple has said it will open source Swift, letting anyone modify it so that it will run on more than just the iPhone and the iPad. When Apple opens up, you'll know the world has changed indeed.