I heard from someone who downloaded Bookcase 0.4 and had problems compiling it. He's using GCC 2.95.3 and apparently it has a couple problems.
First, in the bookcase/src/bcunititem.h file, near the end of the file, GCC was complaining about casting the const char* to a QString so change the "_" to QString("_"). Secondly, it doesn't like the default namespace :: identifier in bookcasedoc.cpp. So just remove those from lines 47, 53, 571, and 572. I'm waiting to hear if that completely fixes the problems, and if so, I'll release Bookcase 0.4.1.
Here are the patches: bcunititem.h.diff and bookcasedoc.cpp.diff
Oh, the things one learns...