Microsoft’s open-source era still comes with an asterisk

Microsoft's relationship with open source has one of the strangest redemption arcs in tech. This is the same company whose former CEO, Steve Ballmer, once described Linux as "a cancer," a line so cartoonishly hostile it still follows Microsoft around like an embarrassing yearbook photo. Two decades later, Microsoft talks about Linux with heart emojis, builds tools developers actually love, owns GitHub, maintains its own Linux distribution, and has open-sourced parts of Windows Subsystem for Linux to the point where one of my editors has stopped picking between Windows and Linux and started running both on the same machine.

The interesting question is not whether Microsoft has changed, because it has. The better question is why it changed and how much of that change survives when open source no longer serves the business plan.

From "cancer" to contributor

Ballmer would not approve (the board did)

To understand the present, it helps to remember how openly hostile the old position was. Ballmer’s famous comment was only a headline version of a broader posture. The company covertly funneled over $100 million into SCO Group's existential copyright attack on Linux, claimed in the media that the open-source operating system violated 235 unnamed Microsoft patents without ever publicly identifying them, and weaponized its legal department to force Linux-based Android hardware vendors into paying lucrative royalty fees. The anti-open-source campaign dates back to Bill Gates' seminal 1976 "Open Letter to Hobbyists," which explicitly scolded early computer enthusiasts for copying Altair BASIC software without paying. So you see, this was not a company with a complicated or passive relationship with open source. It was a company that treated open source like an existential threat to its monopoly business model, to be aggressively litigated into submission.

Then Satya Nadella took over in early 2014, and the script flipped so fast it should have given industry observers whiplash. In October of that year, the newly minted CEO stood before a slide that declared, "Microsoft loves Linux." Over the next few years, Microsoft systematically open-sourced its flagship developer tools, including PowerShell, Visual Studio Code (even though the VS Code you download from Microsoft isn't actually open source — more on that later), and ChakraCore — the original JavaScript engine for Microsoft Edge. More than a decade after Ballmer had compared the Linux community to Communism and a cancer, the company joined the Linux Foundation at the highest Platinum membership tier. It went so far as to build its own internal Linux distribution, CBL-Mariner (now officially rebranded as Azure Linux), to power its container infrastructure, and in 2018 spent $7.5 billion to acquire GitHub, the very home of modern open-source development.

Microsoft president Brad Smith even did the ultimate public mea culpa. Speaking at a retrospective MIT event in May 2020, Smith explicitly confessed that "Microsoft was on the wrong side of history when open source exploded at the beginning of the century, and I can say that about me personally." Credit where it's due: that takes some serious nerve to say out loud for an executive who spearheaded many of those early legal battles. Today, Microsoft boasts hundreds of open-source projects under the umbrella of the .NET Foundation, and its presence on GitHub has grown far beyond early expectations, with over 25,000 internal engineers actively committing code to open-source repositories.

I don't doubt any of these facts because they are well-documented shifts in corporate strategy. What I doubt is that any of it was driven by a sudden flash of principle rather than sheer, cold necessity. Corporations do not typically undergo moral awakenings; instead, they respond to changing market conditions. And the market, around 2011, was sending Microsoft a very clear, existential message: Windows had lost the smartphone war to iOS and Linux-backed Android; AWS was completely dominating the cloud landscape; and if Microsoft refused to run Linux workloads natively on Azure, its cloud business would die on the vine.

Open at the front, locked at the back

Free, as in "free to use our cloud"

What I think actually happened is that Microsoft looked at where the industry was heading, realized it was about to get left out of the most important infrastructure shift in a generation, and made a calculated decision to get on the right side of a trend it could not beat. A Microsoft executive eventually confirmed this without much shame, saying the company "had to embrace open source because customers demand it." Not "because it was right." Not "because we believe in it." Because customers demanded it.

The GitHub acquisition makes that strategy especially clear. Microsoft paid $7.5 billion for the social and technical infrastructure of global software development, and the bet paid off spectacularly. By 2024, GitHub was generating $2 billion in annual revenue, with Copilot accounting for 40% of that growth. The platform now hosts over 180 million developers and 630 million projects. In other words, I would say what Microsoft bought was a tollgate. The open-source world remained accessible, but many of the most valuable services built around it now feed directly into Microsoft's commercial infrastructure.

This is also how Microsoft open-sources things: strategically, and with one hand on the proprietary latch. When GitHub released the GitHub Copilot Chat extension under the MIT license in 2025, developers celebrated. But the core backend services and large language models powering Copilot remained proprietary. The strategy is fairly easy to spot: release what builds ecosystem loyalty and counters rising rivals like Cursor or Windsurf, protect what generates profit.

Then consider the detail Microsoft loves to lead with at tech conferences: more than two-thirds of Azure customer compute cores now run Linux workloads, and Linux underpins services including OpenAI's ChatGPT, GitHub, and Microsoft 365. Microsoft presents this as proof of open-source commitment, and in a narrow sense, it is. But Linux running on Azure is not Linux running free. Azure is a proprietary platform, and Microsoft has even deep-rooted itself into this ecosystem by developing its own Linux distribution, Azure Linux, specifically optimized for its cloud. Widespread open-source adoption of it ultimately deepens dependency on Microsoft's cloud rather than reducing it. Every Linux workload migrated to Azure is another enterprise wired into Microsoft's billing cycle, its support contracts, and its ecosystem of add-on services.

Microsoft loves open source. Read that again

I am not arguing that Microsoft is the same company Ballmer ran. It isn't. The contributions are real; the tooling is genuinely excellent, and VS Code alone has done more for developer productivity than most open-source projects ever will. I use it myself without resentment.

What I am arguing is that there is a version of "we love open source" that means freedom, and a version that means "we have found a more elegant way to own the ecosystem." Microsoft has mastered the second version so well that most people have stopped asking which one it is.