[ajross]

No idea about code commonality, but the broad architecture of WSL is basically the same as the original POSIX personality from the 90's. The "foreign" process runs in a special mode and handles a different set of system calls via a different dispatch mechanism in the kernel, but still on top of the same set of kernel functionality beneath that.

[xorblurb]

Traditional NT personalities were about the mechanism details.

Otherwise it is very current in operating systems to have a common kernel running different kind of userspace using different API - so of course there are some similarities, but only because it would be completely impossible not to have some.

[pjmlp]

Actually they are using the picoprocess ideas taken from Drawbridge research.

You are partially right, it is just that they improved a few things.