Microsoft has always had an awkward relationship with Linux specifically and with free software in general. Maybe awkward isn't exactly the right word. For many hackers and hobbyists, their first real exposure to Microsoft and its then-CEO Bill Gates came way back in 1976, when he accused others in the then-nascent market for personal computing software of stealing his company's products.

"As the majority of hobbyists must be aware, most of you steal your software," Gates wrote in an infamous open letter. "Hardware must be paid for, but software is something to share. Who cares if the people who worked on it get paid?"

Over the ensuing 20 years, of course, Microsoft experienced the kind of double-digit growth and open skies that we now associate with companies such as Apple and Google, and at the end of this run it dominated the PC market in ways that even Apple and Google can't today muster in their own markets.

But not coincidentally, perhaps, the mid-1990s was also the age in which Linux came of age. First conceived in 1991 by hacker Linus Torvalds as a way to mix a free version of UNIX with ubiquitous Intel x86-based PCs, Linux started slowly but gained steam within a few years, jumpstarting a new market, creating companies, and establishing a legitimate contender to both proprietary UNIX vendors and to Microsoft in the server market.

Linux hit my radar in the mid-1990s, just as I was beginning my WinInfo newsletter. Eager to be less tunnel-visioned and open up readers to non-Microsoft technologies, I also wrote about Linux (and other companies such as Apple) and began experimenting with early Linux distributions such as Slackware, which was then shipped out on large sets of floppy discs.

Linux scared the crap out of Microsoft for the same reason it excited me: What, I thought, would happen if Linux could successfully provide a Windows-like experience, but for free? And what if the Linux community could somehow come up with an Office competitor that provided just the most important 20 percent of the features we had all come to expect from the Microsoft solution?

What indeed. These fears drove over a decade's worth of strategy at the software giant and were no doubt part of the reason Microsoft found itself in antitrust courts around the world, accused of anti-competitive behavior. In fact, things got so dicey that Microsoft sponsored a project to port its Office productivity suite to Linux, a project that ultimately never saw the light of day. But it existed. You bet it did.

In 1998, internal Microsoft memos called "The Halloween Documents" by scared open-source partisans were leaked to the web. In what can only be described as a very credible internal assessment of Linux made during a time when many were simply ignoring this system, Microsoft determined that it was a credible threat and should be countered. And in 1999, Microsoft published a site called "Linux Myths," in which it argued, conversely, that Linux was in fact not a threat to Windows NT because Microsoft's products were so much more capable and mature. Curious.

What's happened since, of course, is that Linux succeeded quite well on the server side, while sputtering on the desktop. And in that same time period, Microsoft's Windows Server went from being the low-cost, easy-to-use alternative to the big iron of the day to being the entrenched, professional, high-end solution favored by big business. And Linux plays the role that NT used to play: It's used by smaller and mid-sized businesses, largely, and while Microsoft can make claims about revenue advantages, the overall server pie is still pretty heterogeneous.

So Microsoft played the intellectual property card, claiming that the open-source OS violated its software patents. And it's gone after every major Linux vendor you can think of, generally achieving settlements in which these firms end up paying Microsoft for what may or may not be actionable IP violations.

And then everything got really messy.

As you are no doubt well aware, the computing landscape is changing rapidly these days, and as I've been opining for years, the future of computing is both mobile and connected. Arguably, that describes computing today: Hundreds of millions of users worldwide interact with computing services not through traditional PCs but via smartphones and, more recently, tablet-based devices. And these devices, so far at least, are not running some variant of Microsoft's ubiquitous Windows software. They're running new, compact systems that are based on non-Microsoft technologies.

The most popular of these systems is Google Android. And Android is based on—you guessed it—Linux.

This is a moving target, but as of mid-July, Google claimed that it is activating an astonishing 550,000 Android devices every single day. Every. Single. Day. (That's up from 400,000 in May. Yes, May 2011.)

This means that Google's hardware partners are selling a combined 16.5 million Android-based devices every month, a run rate of almost 200 million devices in a year. If accurate, that's about half the size of the entire PC market. And unlike that PC market, which has slowed considerably in recent years, the market for devices is growing fast. Very fast.

So. Remember that story where Windows beat Linux on the PC desktop? It's true, yes. But it's somewhat ironic that the OSs Microsoft vanquished on the desktop are now coming back to haunt it in the mobile space. (Apple's iPhone is based on iOS, which is derived from Mac OS X. And while Apple continues to sell a decent number of these machines, the Mac still accounts for well under 5 percent of the entire PC market.)

Not so ironic: Microsoft is now suing Android vendors, just as it did with Linux vendors, again for IP violations. The results have been similar: Many Android vendors have simply caved to Microsoft's demands and started paying licensing fees. Some cases remain open.

The odd bit about all this is that while Microsoft is busy reaching for the low-hanging fruit in the open software world—Linux and Android vendors that simply can't afford to fight off a Microsoft legal threat—it has also been collaborating with various Linux companies and opening up support for some Linux technologies in its own products. For example, Microsoft explicitly supports certain Linux distributions in its Hyper-V virtualization platform and allows third parties to build Linux features into its management products. Coincidentally, this very week, the software giant announced an extension of a "strategic relationship" with SUSE to collaborate on Windows and Linux interoperability and support.

I'm guessing this behavior is seen as two-faced by many in the open-source world. But from Microsoft's perspective, it's just simple pragmatism. The software giant knows that its business customers have heterogeneous environments and expect interoperability. And as a commercial enterprise, not a charity, it is required to protect its patents. So this all boils down to simple competition.

But then there's the curious case of the video. This past week, in celebration of Linux's 20th anniversary, Microsoft Germany created a strange little video called Microsoft vs. Linux in which it lightheartedly recounts the history of their often antagonistic relationship. "Microsoft vs. Linux?" the video asks. "Or is it Microsoft and Linux?"

I think this is exactly the question open-source backers have been asking themselves for years. But really, the answer hasn't changed at all. It's isn't Microsoft vs. Linux or Microsoft and Linux. It's both.

Happy birthday, Linux.