I realise that I can't access Form controls from the DoWork event handler of a BackgroundWorker. (And if I try to, I get an Exception, as expected).

However, am I allowed to access other (custom) objects that exist on my Form? 

For instance, I've created a "Settings" class and instantiated it in my Form and I seem to be able to read and write to its properties.

Is it just luck that this works?

What if I had a static class? Would I be able to access that safely?