The Linux kernel underpins
Windows 11. It would be significantly more surprising news than Richard Stallman making a lecture at Microsoft headquarters, rather than Microsoft's Windows NT kernel.
Linux is a free and open source operating system based on Unix standards that includes both a programming and user interface interface. It also includes a number of independently produced elements that are free of proprietary code.
Linux is an open source operating system, whereas Windows is a proprietary operating system. Linux has access to the source code and can change it to suit the needs of the user, but Windows does not.