There is CodeCity written in VisualWorks. Looks like there were some issues with licensing for commercial use.
Now there is a similar tool called "SourceCity" for Pharo.
Have a look at the demo video.
Unfortunately it will not be open source - according to Stef:
"Now we are developing since more than six months a replacement from scratch but it will not be open-source. Interested people will be able to contact us and we will license them the software."
Sad - it would have been a nice example for using NativeBoost. But meanwhile Igor wrote some documentation for NativeBoost using the HelpSystem.