This appendix provides some brief statements about Windows 8 which were not explicitly covered in the article.
All versions of Windows 8 are closed for Metro apps, not just Windows RT. Although aggressively disputed by a number of people outside Microsoft, the truth according to Microsoft itself is that no final version of Windows 8 will allow free dissemination of Metro apps outside of enterprise domains. I have documented this meticulously in Appendix B.
But even if Windows RT was the only version of Windows with a closed ecosystem, this would still be extremely troubling. Windows RT could turn out to be the most popular Windows version in the tablet or phone spaces, and we need openness in those spaces just like we need it on the desktop. There is no reason to believe we should care less about the policies Microsoft implements on Windows RT than on rest of the Windows line.
Even if the Windows 8 UI debuts poorly, that does not mean it won't eventually become standard. In 1990, many (if not most) serious computer users probably thought Windows 3.0's interface wasn't very good either. But 10 years later, its direct descendent was ubiquitous. So regardless of what Windows 8's UI looks like today, simply because people don't like it or don't see its future doesn't mean its grandchild might not be the dominant paradigm down the road. By that time it will be far too late to convince Microsoft to open its distribution model.
People who do not prefer to use the Windows 8 operating system may still be hurt if it remains closed. If Windows 8 becomes popular, most users will be forced to use it at least occasionally (such as at work), and most developers will be forced to support it due to market pressure. People who dislike the operating system will need it to be as open as possible so that they can install software that replaces features they feel are implemented poorly, something that may well be disallowed by future Windows Store policies (policies similar to these exist in the Apple App Store requirements already, for example).
The fact that iOS is a closed platform is more reason to demand Windows 8 be open, not less. The fact that iOS is closed is actually the main reason why Windows 8 for tablets and phones must be open. If iOS were itself open, developers could go write whatever they wanted for the iPad and iPhone, and they wouldn't have to care what Microsoft did. It's precisely because iOS is closed, and Apple has repeatedly denied developers the right to distribute many kinds of interesting and commercially viable software there, that it is essential to have another powerful player in the space that's committed to open software distribution.
Contrary to popular belief, Android, Nook, and Kindle Fire aren't actually closed distribution platforms. Android, Nook, and Fire are all actually the same at the core (Android). Although they all have stores similar in behavior to the Windows Store, all three also allow you to install uncertified APKs (program package files) directly from the web. Granted, it is not exactly a well-oiled process on all of them, so in that sense their platform owners could do more to encourage open distribution. But at least they have not physically prohibited it, as Microsoft is doing with the new Windows 8 ecosystem.
Closed third-party stores like Steam are substantively different from operating systems which require all software to come from a single store. The crucial difference between the Windows Store and Steam is that Valve doesn't own the underlying platform. Any developer can ship a distribution system like Steam to compete with Steam, and any Windows user could install it at the click of a button. The problem with Microsoft owning the distribution on Windows is that once the user has purchased a Windows machine, they cannot simply install, say, an Android system alongside it that they can effortlessly switch back and forth between instantly, as would be the case with Steam and a would-be competitor.
That said, Steam should be opened as well, but that's an article for another time. In brief, what we really want is open Windows and open Steam, and we're certainly not going to get there by having closed Windows and no Steam. That's what we'll have on Windows RT, and as I argued in the article proper, probably also Windows and Windows Pro down the line.
So we should certainly continue pushing Valve to open up Steam to all developers, but pushing Microsoft to open up Windows is more pressing because once it closes, there's nothing a third party can ever hope to do about it.