WPF non-Modal Dialog Boxes

Depending on what framework you are using this is either easy or difficult.

We are using
using Caliburn.Micro;

This makes life a lot easier to do this. The code snippet is as follows:
IoC.Get<IWindowManager>().ShowWindow(viewModel, null, settings);

The modal equivalent is:
IoC.Get<IWindowManager>().ShowDialog(viewModel, null, settings);

Why WPF out of the box does not easily support non-modal dialogs I don't know. MFC, Qt, Fox all do fairly easily.