WinRT With VS2010 On Win8?

To what extent is it possible and legal to developer WinRT applications with VS2010 Pro? On the one side, I think it should be perfectly possible and legal to create an HTML5/CSS

Solution 1:

See here.

You can use the Windows SDK, along with your chosen development environment, to write Windows Store apps (only on Windows 8)...

So it's clearly legal. I haven't tested it, but I'm going to guess that you can probably do the code side of things in VS 2010, but VS 2010 isn't setup to do Windows Store UI so xaml, html5 etc probably won't work.

It's probably much easier to simply use Visual Studio 2012 express.

Solution 2:

To what extent is it possible and legal to developer WinRT applications with VS2010 Pro?

It is not (directly). The APIs and the packaging tools will not be available in VS 2010.

While you could potentially do this yourself, it seems far simpler to just install Visual Studio 2012 Express for Windows 8 and use it.

These days, the IDE seems to be married to the compiler so I'm not sure if the user is allowed to use older IDEs (such as VS2010) to link against newer libraries like those offered in WinRT

It's more than just newer libraries - there's an entire new runtime, and the language needed changing in order to work with it.