Looks like MapWindow can be used as a map control. It is based on C/C++/OCX implementation (a bit old but very fast). Plus authors are currently busy with full C# version. Everything is licensed under MPL.
The new Sandcastle January 2008 Release provides the possibility to make a website (ASP.NET pages) for the documentation.
The Verkenner plugin has been developed 'on-the-job' in DelftShell firstly for the Delta region (Zeeland, Brabant, Zuid-Holland). A second application has started for the IJsselmeer region as well. The Verkenner plugin aims at 1) bringing together information in text (making use of wiki) and maps and 2) analysing the effects of scenarios (measures) on different spatial function such as nature, water quality (WFD/KRW), fresh water supply, shipping, recreation, etc. The Delta-Verkenner can play an important structuring and supporting role in spatial policy processes.
Delta-Verkenner screenshots:
Add or change criteria
Screen to compose an alternative (select external factors and measures)
Map file with several layers
Opening screen: to the left the project tree; to the right the Delta-verkenner wiki