Actually, they even include Windows 7, not only 8 or 8.1 [0]. I guess that "for the first year" will probably be extended as well...

Edit: if this [1] reuters article is true (I couldn't find a reference on Microsoft's site), they are also including pirated versions...

[0] http://windows.microsoft.com/en-us/windows-10/about

[1] http://www.reuters.com/article/2015/03/18/us-microsoft-china...