1998–2016 · Microsoft

Microsoft vs Linux: from “cancer” to Linux Foundation member

Last reviewed 5 October 2026

For a decade Microsoft treated Linux as its biggest threat, with leaked memos, cost studies and patent claims. Linux supporters answered every round, and in the end Microsoft joined them.

The threat appears

By the late 1990s Linux was running a growing share of web servers, and Microsoft noticed. In 1998 a set of internal Microsoft memos analysing open source, soon nicknamed the Halloween documents, leaked and were published with commentary by the open-source advocate Eric Raymond. They described free software as a real competitive danger and discussed ways to counter it.

The rhetoric sharpened in public. In a 2001 newspaper interview Steve Ballmer, then Microsoft’s chief executive, described Linux as “a cancer” because of the way the GPL licence attaches to code it touches. The line became one of the most quoted remarks in the history of the rivalry.

Get the Facts

From 2003 Microsoft ran a marketing campaign called Get the Facts, built around commissioned studies that argued Windows Server had a lower total cost of ownership and better security record than Linux. Each new study was followed by rebuttals from Linux vendors, user groups and analysts, who questioned the methods, the hardware compared and who had paid for the research.

The arguments sometimes ended up with regulators. In 2004 the UK Advertising Standards Authority ruled against a Microsoft magazine advert claiming Linux was far more expensive to run than Windows, because the comparison set a mainframe against ordinary Intel servers. Exchanges like this, with Linux users answering each claim point by point, were a regular feature of the tech press in the mid-2000s.

Patents and the Novell deal

In November 2006 Microsoft signed an agreement with Novell, owner of SUSE Linux, covering interoperability and a promise not to sue Novell’s customers over patents. Many in the free software community saw it as an attempt to divide Linux distributions into “safe” and “unsafe” ones. The Free Software Foundation responded with patent terms in GPL version 3.

In 2007 Microsoft said that Linux and other open-source software infringed 235 of its patents, without saying which. It never sued over the claim as a whole, but it went on to sign patent licences with a number of device makers that used Linux, including many Android phone makers.

The turnaround

The relationship changed after Satya Nadella became chief executive in 2014. Microsoft announced that it “loves Linux”, released .NET as open source, began running Linux widely on its Azure cloud and added the Windows Subsystem for Linux to Windows 10. In November 2016 it joined the Linux Foundation as a top-tier member, and in 2018 it bought GitHub.

Seen from today, the fight looks like a company slowly learning that it could profit from the platform it once tried to stop. At the time it was one of the defining technology rivalries of the decade.