In a way, every OS is trying to be a Windows-like OS? Maybe not at the binary level, like ReactOS, but at the UI level, there's not a whole lot of difference between OS X, Ubuntu and Windows 7.
Even Microsoft has had a hard time trying to make a "better" windows than windows. Every time they try to make any noticeable "improvements", they get an internet full of people screaming at them to "go back to the way XP did it!"
I think the real question should be, is anyone out there working on a
non-Windows-like OS?
On a related note, I just bought my first Windows 8 phone today, just to play with, and I'm amazed at how "almost exactly" like an iPhone it is. Android, Windows Phone, and iPhone have all been copying each other for years now, and the end result is that none of them really stand out anymore. And if Windows 10 is any indication, we'll probably never see any phone (or OS) try to go it's own way ever again. I doubt that we'll see any new innovations until the next big gadget hits the market, whatever that may be...