If you believe Satya Nadella, then Microsoft loves Linux.

Under Nadella’s leadership, Microsoft has a discovered a new enthusiasm for open-source software, leading it to join the Linux Foundation and build support for GNU/Linux directly into Windows 10.

Yet, in some quarters, there is disbelief that a company whose former CEO described Linux as a cancer could be reborn as a true believer.

The greatest suspicion is reserved for the Windows Subsystem for Linux (WSL), which allows Windows 10 to run various GNU/Linux distros and software.

Stories about WSL regularly attract comments and Tweets referring to Embrace, Extend, Extinguish, a commercial strategy that a US anti-trust hearing was told Microsoft used to “smother” the Netscape web browser in the 1990s.

Opinion as to why Microsoft has changed its tune vary, from open-source operating systems being too popular on cloud platforms and on servers for Microsoft to sensibly ignore, to suspicion that this is part of a plan to undermine the use of Linux in the long run. But what do key members of the open-source and free-software communities think?

Richard Stallman is a free-software activist and creator of the GNU OS that forms part of the basis of modern GNU/Linux distros. He believes that Microsoft’s decision to build a Windows Subsystem for Linux (WSL) amounts to an attempt to extinguish software that users are free to run, copy, distribute, study, change and improve.

“It certainly looks that way. But it won’t be so easy to extinguish us, because our reasons for using and advancing free software are not limited to practical convenience,” he said.

“We want freedom. As a way to use computers in freedom, Windows is a non-starter.”

SEE: How Mark Shuttleworth became the first African in space and launched a software revolution (TechRepublic)

Stallman’s suspicion of WSL and Microsoft’s intended purpose isn’t shared by Mark Shuttleworth, the man who kickstarted the creation of the GNU/Linux distro Ubuntu back in 2004. For Shuttleworth, Windows’ embrace of GNU/Linux is a net positive for open-source software as a whole.

“It’s not like Microsoft is stealing our toys, it’s more that we’re sharing them with Microsoft in order to give everyone the best possible experience,” he says.

“WSL provides users who are well versed in the Windows environment with greater choice and flexibility, while also opening up a whole new potential user base for the open source platform.”

The battle for an open desktop

Shuttleworth is founder and CEO of Canonical, the company that produces Ubuntu. Canonical has been a supporter of the Windows Subsystem for Linux since before its launch, working with Microsoft to develop a version of Ubuntu that worked on WSL for its debut in 2016.

Canonical’s willingness to collaborate with Microsoft reflects just how much Shuttleworth’s attitude towards Windows has changed since he announced Ubuntu. At that time Shuttleworth pitched Ubuntu as a challenger to Windows’ dominance of the desktop OS market, a situation he then described as a “bug”.

In the intervening years Ubuntu didn’t become the most popular desktop OS, today accounting for a portion of the roughly two percent of desktop machines running GNU/Linux, although it is very widely used as a guest OS on public cloud platforms, and as a host OS on servers.

Today Shuttleworth takes Microsoft’s newfound enthusiasm for GNU/Linux at face value, and says the company has a different ethos to that of the 1990s, a fresh perspective that benefits Microsoft as much as it does open-source software.

“Microsoft is a different company now, with a much more balanced view of open and competitive platforms on multiple fronts,” he says.

“They do a tremendous amount of engineering specifically to accommodate open platforms like Ubuntu on Azure and Hyper-V, and this work is being done in that spirit. It’s super-impressive work, and testament not only to their engineering but also to the rigour in the Linux kernel community that maintains crisp and stable syscall interfaces over time.”

An existential threat to free software?

Stallman remains adamant that the WSL can only help entrench the dominance of proprietary software like Windows, and undermine the use of free software.

“That doesn’t advance the cause of free software, not one bit,” he says.

“The aim of the free software movement is to free users from freedom-denying proprietary programs and systems, such as Windows. Making a non-free system, such Windows or MacOS or iOS or ChromeOS or Android, more convenient is a step backward in the campaign for freedom.”

The WSL allows Windows users to install GNU/Linux distros from the Windows Store, giving them access to apps for Ubuntu and openSUSE, with Fedora due soon, and other distros due to be added over time.

At present, the WSL has many disadvantages over a running a dedicated GNU/Linux system. Microsoft doesn’t support desktop environments or graphical applications running on WSL, and also says it is not suitable for running production workloads, for example an Apache server supporting a website.

But WSL is also a work in progress, and Microsoft seems determined to make it more attractive to software developers, a group far more likely to run GNU/Linux than your typical computer user.

In responding to Stallman’s charge of WSL being an attempt to extinguish free software, a Microsoft spokesperson reiterated the company’s goal of making Windows the only platform software developers need to use.

“Microsoft aims to make Windows 10 the best development environment, regardless of the technologies that developers use, or the platforms they wish to target. Using Windows 10, developers enjoy the freedom to choose the tools that they want, need, or prefer, whether they’re commercial or free, closed or open source, or any combination therein,” she said.

By adding certain elements of the Windows Subsystem for Linux Microsoft also does seem to be laying the groundwork to extend what’s possible with a single GNU/Linux distro today, for instance, letting the user chain together commands from different GNU/Linux distros with those from Windows.

Windows is already the most popular OS among developers, according to Stack Overflow’s survey of more than more than 64,000 programmers, used by 41% of respondents, with Linux the next most popular and used by 33%.

If Microsoft realizes its ambition to build the best GNU/Linux tools into Windows, then will users still want to run separate Linux operating systems? Yes, says Shuttleworth, who believes that WSL will only serve to broaden the appeal of Ubuntu and other Linux distros.

“Native Linux is useful and people will continue to use it,” he says.

“We very much expect Ubuntu users to continue using our platform as a standalone installation. Within the development space, many of these users are already working in an entirely Linux-based environment and, as such, it seems unlikely that they would redevelop this environment from scratch in order to accommodate a Windows-led approach.

“Many of our users already work on a wide variety of platforms and devices, with Ubuntu sitting alongside other technologies for maximum effect. Personally, I expect WSL to have a very positive impact on open source development.”

For Stallman, however, the question of how WSL might affect GNU/Linux uptake is not worth considering, he simply wants to remind computer users of the broader moral imperative for users to reject proprietary software.

“When the issue concerns freedom vs injustice, speculation about what people ‘will’ do is a side issue. The important question is what we can do, and ought to do, for a free society.”

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