The easiest way to get started with pythonocc: a 10*20*30 box. The first step towards complexity.
STEP Application Protocol 203 (aka AP203) is the most secure way to export CAD data from one software to the other.
Visualization in the browser using X3D/x3dom is just amazingly simple !
Both build system and runtime are multiplatform: the same code base can be executed whether you run OSX, Linux, Windows or both of them.