To build .xml documentation from source:

1) Open OSGeo.MapGuide.Maestro.sln solution
2) Right-click on OSGeo.MapGuide.MaestroAPI project and select Properties option
3) Click on Build tab
4) Check XML Documentation file and type: OSGeo.MapGuide.Maestro.xml
5) Save project settings

To build .chm from autogenerated .xml file:

1) Get NDoc 2.0 (http://www.kynosarges.de/NDoc.html)
2) Open MaestroAPI.ndoc
3) Run Documentation->Build option