No - this is a whole new thing.
The Windows POSIX subsystem which shipped in NT 3.5.1 was a minimal implementation of POSIX syscall API plus a userland toolset. That was replaced with Interix which was renamed Services for Unix (SFU) which had a more comprehensive kernel implementation and more up to date userland. However that tech was not resurrected to build the Windows Subsystem for Linux (WSL).
Importantly, WSL doesn't ship with a distro - we download a genuine Ubuntu userland image at install-time and then run binaries within it.
> Importantly, WSL doesn't ship with a distro - we download a genuine Ubuntu userland image at install-time and then run binaries within it.
So can we use WSL by itself and pick a different distro, if we'd rather use say Alpine or openSUSE or Arch's userland?
> However that tech was not resurrected ...
I, for one, would like to see it resurrected. It's exceedingly useful, and is one major reason that I am not, nor will be, using Windows 10. This new subsystem does not have the things that I use SFU/SFUA for. Nor does it have the BSD-style toolset of SFU/SFUA.