Wow, someone already did the GPDL engine part? That's great!
Maybe tell him about the wxWindows thing to help with the rest of it, if it is useful and makes things easier...
Hmm... 4000 to 6000 pages? Eeeeep!...
(As for the source for GNU/Linux - this isn't available at SourceForge? I would like to know how to compile/install in general, that kind of thing, though.)