> The Xbox OS isn't "a custom version of Windows 2000". They took the networking stack and a couple other bits from NT, but otherwise it was built from scratch.

From the whole Win2k obviously not, and it is common for journalists to not be very precise, but at least the kernel seems to have tons of architectural similarities with the NT kernel, and I would not be surprised if it was a derivative?

https://xboxdevwiki.net/Kernel

I also found https://books.google.fr/books?id=-8YlaRclj2gC&lpg=PA603&pg=P... and that's pretty much what I expected. But nobody who knows the difference about kernel vs. whole windows OS think that they would take explorer.exe and random obscure IT stuff and so over, and 150k is not crazy big, but for a core OS kernel this is completely expected.

The high level API seems to be based on a subset of DirectX and even a few pieces of Win32, so that's not completely unrelated either. It's obvious that the GUI was not taken from Windows, that you won't be able to maybe install a printer and so over, and it is probable that tons of custom code was also written, but that does not make the relationship disappear completely.

The scheduler is radically different and that has knock-on effects on the rest of the OS. The OS gets a fixed time slice every frame before control is handed back to the game. The security model is engineered to distrust the user of the device as an anti-piracy measure.

It might be a derivative, but calling at a “custom version of Windows 2000” is absolutely wrong.

There are also custom scheduling policies in the XBox One IIUC. I agree that a “custom version of Windows 2000” for the original XBox is wrong, but it is not extremely consequential in this article, I can see where it comes from, and I don't think its erroneous enough for it to be a big deal to be presented like that to the public; only experts will find the distinction interesting.

Saying it is a custom version of Mac OS, I would call it absolutely wrong. Here, just wrong is enough :p