Telling only part of a story can be worse than keeping completely mum, as Microsoft officials seem to be discovering with Windows 8.

Last week during the first public preview of the Windows 8 user interface, Microsoft officials said that new Windows 8 apps will be created in HTML5 and JavaScript. By deciding not to mention anything about .Net and Silverlight -- telling developers they'd have to wait until the September Build conference to hear more -- company officials ended up setting off new speculation that the company is poised to dump its current frameworks and programming interfaces.

(If you don't think Microsoft's developers are worried, I'd point you to this post about the future of Silverlight on the Silverlight Forums site, which had lots of vitriolic comments and more than seven million page views before the thread was locked and new threads complaining about Microsoft's lack of information were started.)

I've blogged before about the XAML layer that Microsoft is building for Windows 8 as part of its "Jupiter" initiative. Yes, it still exists, I hear from my contacts. And yes, this will enable support of native Silverlight applications. (Does this mean Windows Phone apps written using Silverlight will be able to run on Windows 8 with no/few tweaks? I don't know.)

Jupiter is a user interface library for Windows and will allow developers to build immersive applications using a XAML-based approach with coming tools from Microsoft. Jupiter will allow users a choice of programming languages, namely, C#, Visual Basic and C++. (Hey, maybe this is why Microsoft is calling the next version of Visual C++ "WinC++"?)

All Microsoft officials said last week was that developers targetting Windows 8 would be using HTML5 and JavaScript and some kind of new software development kit to build immersive apps. By leaving out any mention of Silverlight, Microsoft execs led many to believe that HTML5 and JavaScript would be the only way to write immersive apps for Windows 8 that will be available via the coming Windows App Store.

Microsoft is still going to support Silverlight with Windows 8, and not only as a browser plug-in, my sources say.

At the 50,000-foot level, Microsoft wants to find a way to reinvigorate the Windows-development ecosystem. (I believe that's one reason the Internet Explorer team has been talking all that "native HTML" nonsense. They really mean they're trying to get developers to write HTML/JavaScript apps that use IE's hardware acceleration for the "best" HTML experience.)

Microsoft's longer-term goal is to align its various developer stacks, giving it a story that's comparable to Apple's. Because Apple supporting iOS on tablets and phones, Apple developers can write once and have their apps run in both places with relatively little modification.

Windows Phones are running the Windows Phone OS, which is currently based on the Windows Embedded Compact kernel (with a whole lot of customization), and Windows 7 on tablets. Microsoft's ultimate goal -- now that Windows 8 will be able to run on ARM -- is to get its phones running on Windows, too. It's uncertain whether Microsoft will be able to pull this off by late 2012, when Windows 8 and Windows Phone 8 are both expected to ship.

At the more granular and immediate level, Jupiter is the way that Microsoft is planning to get developers to write new "immersive" applications for Windows 8 that will use the IE 10 rendering engine while using the .Net and Silverlight technologies they already know. Jupiter is aiming to provide these developers with a managed code XAML library, so that developers can access the sensors, networking and other Windows 8 elements in a way to which they're accustomed.

Applications built using Jupiter won't be targeting the "classic" mode/shell that Microsoft showed off last week during its Windows 8 preview, I hear. They'll be the same class of immersive apps targeting the new Modern Shell (MoSH) that Microsoft will be writing itself and/or trying to convince others to write using HTML5 and JavaScript.

It definitely seems Microsoft's ultimate goal is to wean developers off Silverlight and to convince them to use HTML5 and JavaScript to write new apps for Windows, going forward. But until there's better tooling for HTML5 (beyond what Microsoft provides via the F12 HTML tools in Internet Explorer), it seems the Softies are going to support .Net and Silverlight via new versions of Visual Studio, the .Net Framework and Expression.

I believe Jupiter is key to enabling Microsoft to continue to insist that Silverlight's not dead (as far as a development platform) -- at least for now. But anything that's not a new Windows 8 "immersive," modern application, going forward, is now going to be considered "legacy," from what I can tell.

All of what I've said here is from sources who have asked not to be identified, not from Microsoft officials associated with Microsoft's Windows or Developer Division. Like many devs I've heard from, I don't believe Microsoft can't afford to wait three more months to let its developer base know what its intentions are. So far, however, ill-advised silence seems to be the Softies' plan....

Update: There've been some Jupiter sightings in a leaked Windows 8 build, as well as a number of Silverlight mentions, for what it's worth. (Thanks to @MossyBlog for the pointer.)