We are wondering about this as well. We had no trouble finding the online documentation but we used to get a local copy of the WPILib documentation (as well as a copy of the source code) when we installed the WPILib updates. Now the documentation only appears to be available online and we have not found a convenient way to grab a local copy... and we do not appear to have access to the source code at all (only header files).
In addition we have just noticed that we cannot have the WiFi connect while connecting the the roboRIO over ethernet. This causes a conflict in being able to view documentation and program the roboRIO on a laptop. Hopefully they will fix this soon by making a soft copy of the Doxygen documentation available as a pdf or similar that can be hosted locally on a laptop.