Kent sent me a mail about this and it's really fascinating stuff. Riverdeep, the company behind The Print Shop is hosting the CLR in their MFC based product in order to take advantage of functionality provided by the CLR. Here's a bit from the intro:
The Print Shop 20 Uses .NET CLR from MFC to Ease into the .NET Framework
The existing 1.4 million lines of code were not structured well enough to turn into COM components or to convert into managed C++. Riverdeep hit on the unorthodox approach of hosting the Microsoft .NET Common Language Runtime inside their MFC-based C++ application, which turned out to work extremely well in practice.