If you are just looking for ANY free 3D engine, I would recommend having a look at either Unity 3D or Unreal Engine 4. While they can be daunting at first because of their versitlity and complex editors, both engines have huge communities and a large amount of documentation to get beginners started.
IDK about Urho3D, but often the smaller 3D engines might also be quite good, but have much smaller communities and sometime quite lacking documentation which might be the bigger roadblock to beginners than the vast amount of features of Unity or Unreal.
Both engines are completly free for personal use nowadays, and any kind of license or royality payments would only apply if you start making serious money with your game. So if you are not into Urho3D because of its opensource nature or because you like to dissect the engines code (and the Unreal Engine 4 code is also available if you want to poke around in it), you might want to reconsider your choice of engines.
DISCLAIMER: I am NOT making any statment about the power or quality of any engine mentioned... I just state the facts about size of communities, which often is just as or even more important to get into an engine than how easy to learn the engine itself is.