Every time InfoWorld does a story that mentions Android's market performance, like my recent article on how Android is displacing Windows in embedded devices, at least one Linux zealot posts a comment saying that Android is really Linux and that Linux is winning the platform war everywhere because of such adoption.
I typically roll my eyes -- Android may use the Linux kernel, but it's not Linux any more than OS X and iOS are Unix because they use a Unix kernel or that Windows used to be DOS because it ran on top of DOS. Android, Tizen, and all the other platforms that run on the Linux kernel are not mere distributions of Linux, as the zealots want us to believe. They go well beyond Linux, and some like Android have strongly resonated with the regular world. Linux never has, despite what Ubuntu and Mint fanboys would like to believe.
But it's very true that Linux is everywhere, not only on the servers where it started and quickly dominated.
Yes, Linux as a desktop OS remains a hobbyist, Tinkertoy-style platform, for people who don't want to run commercial apps but command-line everything. Linux blew its chance to be a mainstream desktop OS when it failed to offer a usable version for regular people when Windows Vista provided the opening. The Linux community didn't want to mainstream their favorite operating system, preferring instead endless arguments over whose distribution is better or purer or crunchier.
But because Linux was both a kernel and an operating system, coupled with the fact that the kernel was separated from the rest of the OS, it meant Linux could be used as more than a traditional computer OS. (Not so much with XNU, the intertwined Unix kernel in OS X and iOS.)
Google's Android is a great example of how that separate kernel let Linux gain adoption well beyond its origins as a server OS, though of course Android relies as much on Java as it does on Linux. (Remember: An OS is more than a kernel, just as it is more than a user interface.)
The Linux kernel is also the basis of Google's Chrome OS, the data-mining giant's attempt to replace traditional PC OSes with a browser. Although Chrome OS has remained a very niche product (very much like desktop Linux), it continues to cast a shadow on the PC world, especially as more cloud services gain adoption and make the notion of an all-Internet computing platform plausible.
Linux is very widely used, though hardy anyone realizes it, as the OS for telephony equipment like PBXs at customer premises. A Linux variant powers TiVo's TV recorders, and another variant powers Linksys routers. A variety of musical devices, from synthesizers to digital pianos run Linux -- so do digital signs.
Other niche OSes -- all struggling -- based on the Linux kernel include the mobile-oriented Tizen, Ubuntu Touch, Sailfish, WebOS, and Firefox OS. These struggles are not a sign of Linux's failure, but of the reality of how hard it is for new platforms to drive out established options. Yes, Linux succeeded in knocking out Unix servers, and Android has outpaced the industry-changing iOS. But those are atypical.
More typical is an effort like Tizen. It's the fourth iteration of the Linux Foundation's effort to create a mobile OS that is not iOS or Android. There was first Moblin, which was merged with Maemo, which became MeeGo, which became Tizen. Each time the mobile Linux effort was rebooted, the mission evolved. Tizen today is more about devices like TVs than about smartphones and tablets, where it has flopped, but that's OK. TVs need OSes too.
The fact is Linux makes it possible for developers to create OSes for all sorts of new things. That is cause enough for celebration by the Linux community, whether or not what the user sees is Linux itself.