bgen currently requires Universal Headers, but doesn't really 
make that explicitly clear.  Universal headers do not come 
with the OS X developer tools.

It's not terribly hard to convert the bgen suites to expect OS 
X style headers.  Attached is an example that extends some 
of the Qt wrapper functionality for a project that I needed.  
It has been modified to accept OS X developer tools headers 
(but not Universal Headers).  It would be possible to make 
generators that could use either, depending on which is 
found, but that was not one of my goals.

Note that macglue.h was not changed, just included so it'll 
build outside of the python source tree (if 
bgenlocations.TOOLBOXDIR is appropriately changed as well, 
of course).

Although this might be seen as a bug in the Python build machinery, I'm 
closing this as a won't fix feature request.

The Carbon bindings are deprecated and will not be updated in the future, 
hence the state of bgen is basically irrelevant.