Microsoft’s Windows Subsystem for Linux has become an important tool for developers and power users since it was introduced in the Windows 10 Anniversary Update back in 2016, giving them access to a built-in Linux command line and Linux applications from within Windows.
The company has steadily improved WSL since then, improving performance, making it easier to install and use, and adding features like GPU and audio support. But today as part of its Build developer conference, Microsoft announced that it would be making almost all of WSL open source, closing the very first issue that the then-new WSL project attracted on Github in 2016.
“WSL could never have been what it is today without its community,” writes Microsoft Senior Software Engineer Pierre Boulay in the company’s blog post. “We’ve seen how much the community has contributed to WSL without access to the source code, and we can’t wait to see how WSL will evolve now that the community can make direct code contributions to the project.”
Only two elements of WSL remain closed-source for now: an lxcore.sys kernel driver used for WSL 1 (the initial version of WSL that is still supported, though new installs default to 2019’s WSL 2); and the p9rdr.sys and p9np.dll files that handle filesystem redirection from Windows to Linux (in other words, making it so that Windows can easily access the Linux filesystem). Microsoft didn’t close the door to open-sourcing those components but also didn’t say if or when it planned to make them open source.