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Comment by petters | Hacker News Reader

Is this legal? It obviously is, but how? I thought the GPL would require Microsoft to ship the Windows source code? I suppose it counts as a separate component.

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> I thought the GPL would require Microsoft to ship the Windows source code?

I'm inclined to think Windows is not a derivative work of the Linux kernel by any remotely tenable legal theory, but anyone with code in the kernel they are shipping willing to take the other side of that bet against Microsoft’s legal team has the option to try.

My guess? Because they aren't linking to it.

Longer guess: I suspect they are doing some fancy virtualization tricks here to service calls directly like they would a VM but in a VERY lightweight manner similar to containers. This fits with other announcements concerning containers that were also made today.

Again this is all supposition without any actual knowledge.

That's a trick the separation kernels and micro-hypervisors (esp OKL4) were advertising years ago:

http://linuxdevices.org/using-a-hypervisor-to-reconcile-gpl-...

Such tricks are one of the reasons I support stronger copyleft like License Zero's Parity. Otherwise, they just loophole their way out of stuff.

> The kernel provided for WSL2 will be fully open source! When WSL2 is released in Windows Insider builds, instructions for creating your own WSL kernel will be made available on Github.

The kernel part will be fully open source, which should be sufficient enough to comply with GPL

(IANAL)

> which should be sufficient enough to comply with GPL

this is an age-old debate. Some people say that it is e.g. legal to make (redistribute to precise) a GPL device driver for windows, and some argue that it is not, because the whole kernel should then be GPL.

> https://linux.slashdot.org/story/02/11/05/0051225/gpl-issues...

The Linux kernel will be isolated by an hypervisor.

But in Windows drivers are binary files which talk to the kernel through an API. Not much different than a binary user mode application. If binary user mode applications written in GPL are ok, then so should this.

> Not much different than a binary user mode application.

well, user-mode applications do syscalls to the kernel, not direct function calls.

But the actual syscall is made by a Windows user mode library - kernel32.dll/... So your GPL user mode app calls directly into proprietary Windows library.

That is specifically allowed by the GNU GPL. See "System Libraries" and adjacent paragraphs.

There is a mention of "System Libraries" in GPLv3, but not GPLv2, which the Linux kernel is licensed under.

There are similar provisions in GPLv2.

It hinges on the definition of "derived work" (anything outside derived work is outside copyright's effects, and the GPLv2 uses only copyright to give it effect). Their WSL2 Linux kernel will clearly be a derived work of the Linux kernel, so they obviously will provide full source code of that; the rest of Windows most probably won't.

Yes, it is perfectly okay to dynamically link with a GPL component from a proprietary component, as long as that component is remains handled as per GPL.

(You kind of need to be able to use GPL code dynamically to be able to run it from a proprietary OS of any kind in any way.)

The same way binary blobs are allowed in the kernel, or Android can ship with proprietary bits, etc...

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