Last week, rumors hit the Internet that Microsoft was going to drop the "Metro" branding when describing the new touch screen user interface for Windows 8. The rumors pointed the finger at a possible copyright conflict. One report claimed that the Metro rebranding was supposed to be announced late last week.
That last bit didn't actually happen and Microsoft continues to happily use the Metro brand in its official blogs. In a new post on the Windows 8 app developer blog, Microsoft talks about how Windows 8 Metro app creators can make their own Windows Runtime components.
The highly technical post goes over some of the reasons why Windows 8 Metro app makers could program their own Windows Runtime components. For example, the blog talks about how developers could use Runtime to put in support for an Xbox 360 controller in an HTML5-based Windows 8 Metro app. Yet another possible use would let developers put in the C# Windows Runtime component in order to allow support of zip files in an file viewer app using HTML.
Microsoft does state:
Not every API you write for your Metro style app should be exposed as a 3rd party Windows Runtime component. In general, use Windows Runtime types when you are communicating between programming languages and use types and constructs that are built into the language that you are using for functionality that is not publicly exposed via a Windows Runtime component.
Source: Windows 8 app developer blog