Jupiter could represent Microsoft's latest enhancement to the Windows development framework, giving it better graphics and making it more suitable for slate and tablet machines. If you can remember back to "Active Desktop" then it might all sound very familiar.
Microsoft is planning another development paradigm shift in the form of a project code named "Jupiter". At the moment it is only rumour and innuendo but it seems to make sense and have substance enough to take it seriously. The prime sort of information on "Jupiter" is the "All About Microsoft" blog written by long-time Microsoft watcher Mary-Jo Foley. Most of the comments reported are just that - verbal comments - so it's not easy to provide hard evidence.
Given the lack of hard detailed information, it is difficult to say exactly what Jupiter is, but it seems to be a user interface layer based on XAML that is built into the Windows presentation layer. The idea is that it will make the Windows desktop support better animation and graphics in general. The suggestion is that this new technology will help Windows become more like a web environment - a web app store for Windows 8 is another rumoured development.
Clearly there is also scope for crossover between Jupiter and Windows Phone 7 which is a Silverlight/XAML based framework. It is worth noting, however, that the basic XAML technology has been available in WPF for some time and yet the only desktop application from Microsoft to make use of it is Visual Studio 2010 - and many developers are quick to complain how slow and buggy it is.
It also seems likely that Jupiter is an attempt to get Windows to work well on slate platforms while keeping a layer of fancy graphics. Given that one of the announcements at the CES was that the next version of Windows will be ported to run under ARM processors - used in phones and slates - this makes reasonable sense. A XAML presentation layer could be a way to create a slimmed down Windows just right for the lower power processors and smaller memory.
One interesting point is that Windows has been down this route once before. Back in the days of Windows 98 Microsoft introduced "Active Desktop" which allowed the OS to mix with web content and applications. Even today there is an underlying HTML based technology that controls how folders are displayed - its just that now no body talks about it and ActiveX as a component architecture is history.
Windows has long needed an easy to use UI framework that allows programmers to work with "the shell" as if it was something more modern - but XAML? With most of Microsoft falling in love with HTML5 even mentioning XAML in this context is strange. Resurrecting the old Active Desktop approach with a more modern markup language might make more sense.
These are early days and Microsoft could well be just canvasing ideas for where to go next. Microsoft (in the shape of Soma Somasegar Senior Vice President of the Developer Division) responded to Mary-Jo's blog by saying that Microsoft didn't want to talk about the next version of Windows and that some of the information in the blog was not right and out of date. So some of it is right and up-to-date. Not so much a denial as an obfuscation.