I'd be surprised if the water mentioned was leaking into a 747 from outside the pressure hull. In my experience water dripping down from the ceiling during flight will be condensation. The other possible source would be potable water pipes, although I don't know where these run in the 747, in most a/c I'm familiar with they are under the floor.
The leaks with the Dash 8 'sunroof' get in when the a/c is parked up and un-pressurised. This is an a/c that does seem to produce alot of condensation however, which then drips from the insulation blankets.