How open or closed are Windows, Mac OS X and Linux?

[billyboy]

I read that MS wont release source code at all at all; people say Linux is great because it is open source; Darwin is open source and there is terminal which I understand is the way into the soft underbelly of Mac OS X. But at the end of the day, are they all the same closed deal at the bottom line, with someone somewhere guarding and controlling the vital bits.

[bousozoku]

According to the reports I've seen, MS Windows (some versions) is available to certain companies and governments in source code. I'm assuming this is some sort of listing and probably is still missing details.

Apple, of course, don't want anyone else looking through Aqua, so it's unlikely that anyone outside of the company will ever see it.

Any one can go through all the various pieces of Linux but since there are few, if any, programming standards, that person will have a bit of fun interpreting the mess. Besides that, different pieces, belong to different groups and will have different styles. There are many GUIs available on top of XWindows (X11R6-compatible XFree86) and all come in source code.