Hello Martin,
You can use Nevron Diagram WinForm controls in WPF applications through the WindowsFormsHost.
We have assisted several customers with their requirements. We have prepared a simple example (attached) for integrating Nevron Diagram for Windows Forms in WPF apps. You will have to update the references.
Please note that If you are using Nevron .NET Vision for VS2010, you must switch the target framework to ".NET Framework 4" as by default the VS2010 applications target ".NET Framework 4 Client Profile".
You can use both Nevron Chart and Diagram for Windows Forms in any WPF application. Following is a nice post about WinForms and WPF: http://www.switchonthecode.com/tutorials/wpf-tutorial-using-winforms-in-wpf