It turns out that the Unicode support for curses did not build correctly on OS X at all. There were two issues:
1. On OS X, unlike many systems, does not supply separate libncurses and libncursesw in /usr/lib; same for libpanel/libpanelw. So the tests in setup.py based on the presence of the "w" libs failed, thus disabling the wide-char support in the extension modules even though the OS X libs supported it. The tests in setup.py are now fixed to handle building on OS X with either the system libs or locally-supplied copies.
2. The 32-bit-only installer has historically built and supplied its own copy of libncursesw so that installer build did find a wide lib. However, the wide code support within ncurses is conditional depending on _XOPEN_SOURCE_EXTENDED which is specifically not defined for OS X (platform=='darwin') builds. That caused the compile errors (things like cchar_t from the ncurses include files were not getting defined). The solution for that is to supply _XOPEN_SOURCE_EXTENDED locally to the _curses* extension module builds.