Peter Dyballa writes:

 > >> that both shared libraries are presented to the application, as
 > >> recorded in the Mac OS X crash dump. I want to avoid this
 > >> situation by statically linking one of them to avoid that the
 > >> application asks for one particular shared library – and gets
 > >> two presented.

That's not what's happening.  I don't understand the Mac OS X dylib
architecture in any depth, but I'm pretty sure that an object can
request an object from a specific location to be dynamically linked
(similar to the -rpath flag in GNU ld).  FWIW, my guess is that the
reason you're seeing multiple instances of libraries is not that Mac
OS X "presents" them, but because

 > 	/usr/X11R6/lib/libXft.2.dylib (compatibility version 2.1.0, current  
 > version 2.1.0)

is specifically requesting a different version from the one you get
from /sw.  Try running otool on /usr/X11R6/lib/libXft.2.dylib and see
if the output corresponds to the unwanted versions.

My experience with Fink is quite old by now (I switched to DarwinPorts
three or four years ago), but it was quite sensitive to this kind of
thing.  In particular, you really really wanted to use Fink's version
of X11 libraries rather than Apple's if you were going to build X11
applications yourself.  Old, FWIW, YMMV (but you're clearly not
getting very good mileage!)