Actually quite some work went into making Nim integrate better with C++ code, C++ templates especially I guess.

No, Urhonimo is not integrating Nim as a "scripting engine" - its a full wrapper of the whole Urho3D C++ library. So its much more complete and allows you to write anything you could write in C++. Modulo bugs we haven't fixed yet ;).

The wrapper is mostly automatically generated using c2nim.

From what I have heard from Araq (who maintains Urhonimo) Urho3D does use some fancy C++ stuff, so it took a bit of work to improve c2nim to handle it. Also, unless I made that clear, the Lua/AngelScript "bindings" are not full bindings of Urho3D - instead they are integrated as scripting engines within Urho3D, although a pretty deep integration and with tons of examples.

And oh, Urhonimo was yesterday upgraded to Urho3D 1.4, but Araq needs to ... clean it up and push it :)