To build libharu as a shared dylib on Mac OS X, modify the Makefile after calling ./configure --shared

Here are the relevant sections and the lines to be changed:

...
CC=cc
PREFIX=/usr/local

LIBNAME=libhpdf.a
SONAME=libhpdf.dylib
SOVER1=.1
SOVER2=.0.0
LIBTARGET=libhpdf.dylib
CFLAGS=-Iinclude -fPIC -fno-common -c
...
$(SONAME): $(OBJS)
$(CC) -dynamiclib -o $(SONAME)$(SOVER1)$(SOVER2) $(OBJS) $(LDFLAGS) -Wl
ln -sf $(SONAME)$(SOVER1)$(SOVER2) $(SONAME)$(SOVER1)
ln -sf $(SONAME)$(SOVER1) $(SONAME)

Now you can build and install:

make clean
make
make install

Test PDF files from pdf-tests.factor are generated in the test folder.