I suspect that large part of Windows, perhaps not the kernel, but many of the required subsystems, are written by 3rd. parties and licensing will prohibit an open source release of Windows.

There definitively are some third party components in Windows, but I believe in the core most is either written directly by MS or at least the copyrighted (or its handling) is transferred to them. Parts of an old NT kernel has already been published for a limited audience (mostly education and research, with some additional prereq and with the need of an explicit licence), so probably it can be done again.

The kernel is full of third party libs too.

They still make money on every single pc/laptop that ships with windows which is still their biggest money maker with office. If they truely open source windows (BSD or else) it will be free to ship for OEM and Microsoft will lose one of their biggest source of income.

tl;dr: not gonna happen

Android is open source, and still (nearly) everybody is locked into Google's version with licensing costs. Google open-sourced nearly everything, while managing to make their "apps" so entrenched that every customer expects them and even a lot of apps don't work without them.

> Google open-sourced nearly everything

Nearly everything about Android the operating system. Android the app platform is deeply tied to Google Play Services, which is not open source and is once more deeply tied to Google's online services.

And they've re-routed apps' access to basic phone data like GPS, camera and microphone through Google Play Services, so that if you want to use any app that uses those services you also have to let Google log those data.

It's almost as bad as tivoization from the FOSS perspective, while also invading your privacy. Yay.

NO no no... Alibaba has a clone that they claim their OS, YunOS, is not Android and even it is not written in java, but can run most of Android apps.The OS is written in some java like programming language and close sourced.

Open source doesn't mean free....

Actually it does mean free to redistribute, this is the essence of the BSD or even GPL licenses. And free to redistribute (for free) would be a huge loss for windows. Therefor, not happening.

Technically not, but look at CentOS. We'd have a knock-off Windows from Samsung or whatever in less than three months.

Edit: Every OEM would have their own spin, for differentiation. Lenovo too...

Be realistic, the next day 10 forks would appear distributing it for free.

Windows is always pirated distributed for free doesn't mean they don't violate copyright laws and other restrictions.

One can buy an oem or restricted region license for windows for 20$ but legally it's about the same as pirating it.

They can give access to the source code without necessarily using an Open Source licence for that.

I'm not sure what would they gain, apart from "internet points" for being Good Guy Microsoft.

If the license isn't extremely restrictive about what you can do with the source and your knowledge of it, it would be a huge boost for Wine and ReactOS. Since those two are the biggest threat to Windows on the Desktop, I don't think Microsoft would risk that.

If it's just the kernel and not the userland above it, I doubt it. Apple's open sourcing of XNU and Darwin was never an existential threat to Apple.

The question is how much third-party code there is in the NT kernel. There may even be remainders of the cooperation with IBM tainting the source code (Windows NT did have an OS/2 personality at some point).

Based on what researchers who had access to the Windows kernel are saying, Windows has a decent amount of edge cases and special conditions to maintain backwards compatability with old software. For example if some popular software from 2000 abused some implementation detail that has since changed, Windows will detect that specific program and simulate old behaviour for it.

I expect most of that stuff lives in the userland interfaces to the kernel, but at least Microsoft seems to consider those to still be kernel code.

If you think of kernel32 & friends, that's not actually considered kernel code. That is the "kernel" of Win32, which is mostly a userspace thing. The word kernel is just used in an overloaded way.

IANAL, but I expect it would open Microsoft up to countless patent, and perhaps copyright, lawsuits.