No, I don't think that you're ready to convert anything to c++. Or you have some problems to express yourself. But what you're saying does not really make sense.
There is only one programming language named C++, with several versions already, but still just one language. There are several compilers for this language out there, and every compiler brings slight modifications to the language (compared to the standard), and some extensions. But the major part is still the same for all compilers. So there's just one c++, and thus Irrlicht is made for all of them. The managed code version Irrlicht.NET is completely different, works only with MSVC.NET versions (so not just the one named as such, but...), and is to be used by C# programmers first of all.
Namespaces can be chosen by the programmer, Niko chose irr as top level namespace (because you may have to type it several times in your code). there is no namspace named irrlicht.
