Microsoft effectively forked Linux here -- some pieces such as integration with the host NTFS filesystems or Direct3D support are unlikely to ever be upstreamed

Microsoft effectively forked Linux here -- some pieces such as integration with the host NTFS filesystems or Direct3D support are unlikely to ever be upstreamed. Yes it's Linux, but not really. Another way you can tell it's not actually Linux: if something is acting up, where do I inspect the source code? Where can I send a PR if I come up with a fix? It's smart that MS bought itself a Linux foundation platinum membership; that probably goes a long way in preempting trademark claims of the 'Linux' name.