Today Red Hat announced that it has become the first $1 billion open source company. Although it’s long been known that Red Hat would hit this milestone soon, it’s a major achievement in the history of Linux and open source. But it also raises the question of what’s next for the little open source kernel that could.

“Linux” originally referred to the operating system kernel built by Linus Torvalds and purists still refer to operating system as “GNU/Linux.” But as distributions of GNU/Linux like Debian and Red Hat took off, many people stopped saying “GNU.” The kernel and basic GNU tools have become so standard and invisible that hardly anyone thinks of them any more – instead we think about different distributions, differentiated by different pre-packaged tools, package managers, desktop environments, etc.

“Distro hopping” is popular with geeks, but the range of choices may be confusing to newer users. As Brian Proffitt pointed out when Mozilla announced Boot to Gecko:

Canonical has been increasingly good at this “masking” of Linux. It give Linux props when it has to, but for years it’s all been about “Ubuntu.” The company is even carrying it one step further with Unity… I hear that term bandied about in the press as a platform in and of itself more than I hear “Ubuntu Unity,” and I think that’s intentional.

Proffitt argues that distributions are becoming less and less important, and that’s being driven by mobile where the fact that the Linux kernel lives underneath Android and webOS is unknown to most, if all users. What’s becoming more important are the user interfaces – Unity, HTC Sense, etc. I think you can make the case that these are still distro issues – ie, that HTC Sense is a Linux distro based on Android. But it’s true that the differentiators between distros is moving up the stack, from low level system tools to package managers to UI environments to variations on specific UI environments.

But that’s all on user facing Linux OSes. Will we see the same thing on servers? Maybe. Look at OpenStack and Eucalyptus. Both are cloud infrastructure platform often referred to as “operating systems for the cloud. But they can run on multiple distros. Eucalyptus vs. OpenStack will become a more important decision than RHEL vs. Ubuntu. And the distro makers are already placing their bets: Ubuntu offers OpenStack, instead of Eucalyptus, by default. And Red Hat has partnered with Eucalyptus. Joyent is getting in the cloud computing OS game with its own Unix-like SmartOS, based on IllumOS (which is based on Open Solaris) instead of Linux.

There’s been some debate over which Linux distribution is most popular in cloud environments, but in truth it matters little. The rest of the stack is more important – the Web server, the programming language, the framework. It’s not about RHEL and Ubuntu anymore, it’s about Nginx, Node.js, Ruby on Rails and Django.

Meanwhile, Apache Hadoop is being referred to as the “Linux of big data.” Hadoop runs on Linux, but has a number of different distributions and many different MapReduce applications can run on top of it. In the big data arena, Linux fades further into the background as data scientists build on Hadoop. And although Microsoft is expected to allow Linux on its cloud service Azure, it’s already running tech preview of Hadoop on Azure which opens a number of possibilities that are even impressing skeptics.

It might be tempting to see Solaris and Windows Azure as threats to Linux, but it’s more about the OS layer disappearing from sight. That’s why Microsoft is focusing on stuff like Azure and Hadoop – if server operating systems become invisible, it needs to have a compelling offering further up the stack. Red Hat seems to be moving in this direction as well with its acquisition of open source storage vendor Gluster and the OpenShift platform-as-a-service.

The Linux distribution, and in fact the entire operating system, may fade into obscurity but of course they won’t go away. There are worse fates for a technology than becoming something so dependable and so invisible as to be taken for granted.