This is correct. The Xsource contains source code for many VFP dialogs like Task pane, Beautify, Class browser, Report Builder, Wizards, etc. Each of above application is in a separate folder and unzipping Xsource ZIP is the whole installation process.
The main reason of Xsource is almost unlimited extensibility of VFP environment and if you would like to contribute you may do it at vfpx.Codeplex.com
Each application has its own project file in appropriate folder, so you may open the project file and look inside. Docummentation is provided in the form of source code comments obviously.
Xsource is also useful if you need to debug some problems in e.g. Report listener etc.
BTW, the VFPSource folder contains 21 subfolders, Wizards folder contains 17 subfolders.
Codeplex.com contains the latest VFP help file also.