All the versions of Windows Vista share the same kernel, correct? All the versions of Windows 7 share the same kernel, correct? How much did MS change the kernel between Vista and Win7? I don't know the answer to this. All this lead me to believe that Vista is one OS and Windows 7 is one OS, and maybe Win7 is just Vista2 (or 1.5). So assuming there hasn't been a drastic change in the kernels, Win7 and Vista are actually one OS.
Think of it as movie with a DVD theatrical release, BR release, a directors cut, and a big box set with all the extras; the underlying story is the same in all versions.
Do we think that Chrome OS and Android will share the same kernel. If they do, then what Google has is one OS. If not, two...