If Microsoft did that they'd have to go after all the other projects that let you run Windows apps (Wine for linux being my primary thought on the matter, but I could be entirely wrong about that, in terms of actual topic accuracy)
Really, all they're doing is supporting Microsoft Windows API calls. So long as they're using their own GUI and making their own code to handle the API calls, everything should be fine. I guess I'd have to check out ReactOS before I could say any more, so I'll stop here.
Suffice to say, it wouldn't be worth MS's time. They have bigger issues (like software piracy) to worry about.
Important Addendum:
VonGodric wrote:Chronos - would you be interested in making a fake-os that internally "functions" as "real" os? You sure could help us...
Sorry for not noticing the above quoted post...for one reason or another I didn't see it. Saw it now, and that's what matters (I hope. *sweatdrop*)
That sounds pretty cool to me. I've managed to make clones of MD, RD, Delete and Type so far, just to see if it could be done. My versions look a bit better than the originals too. (That is, if I didn't inadvertantly delete them when I cleaned up my USB flash drive. If I did, there's always a rewrite, which I really don't mind doing. :P) I've actually been wanting to implement a scripting language, but I don't have enough knowledge of language development to do so. But hey, this sounds like something right up my alley, so I'll give whatever help I can. :D
I don't know how much time I'll have to dedicate to the project (moved August 1st and a lot is still going on, even 2 days from the first of October), but I'll definitely put what time I can into it.
Another addendum:
And I am, by no rights, an advanced programmer. I know BASIC-likes pretty well, but the C++ course I took in high school (including knowledge on pointers and using them) eludes me. I know what they are, and what they do, but using them is a little past me at the moment. Always willing to re-learn, though, so if I'm need to utilise them I'm sure there are good internet resources to look at.