These files may help you while developing a script or addon for XBMC, since it will enable IDEs to perform auto completion of class and method names, and also provides you with the documentation for each class and method.
Typically you can add a "source directory" to your development project, and then point it to the folder containing the xbmcstubs files, and you will then be able to "import" the classes as you normally would in Python.
Bug reports are very welcome, they may be submitted through the GitHub bugtracker.