Finally i think the zlib installation failed too, which is neccesary to use libpng.

But make test and make install didn't fail here:

[localhost:/Library/libpng] miklas% make test
./pngtest
Testing libpng version 1.0.12
with zlib version 1.1.3

libpng version 1.0.12 - June 8, 2001
Copyright (c) 1998-2001 Glenn Randers-Pehrson
Copyright (c) 1996, 1997 Andreas Dilger
Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
library (10012): libpng version 1.0.12 - June 8, 2001 (header)
pngtest (10012): libpng version 1.0.12 - June 8, 2001 (header)
sizeof(png_struct)=1272, sizeof(png_info)=288
Testing pngtest.png:
Pass 0: rwrwrwrwrwrwrwrwrw
Pass 1: rwrwrwrwrwrwrwrwrw
Pass 2: rwrwrwrwrwrwrwrw
Pass 3: rwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrw
Pass 4: rwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrw
Pass 5: rwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrw
rwrwrwrw
Pass 6: rwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrw
rwrwrwrwrw
PASS (9782 zero samples)
Filter 0 was used 21 times
Filter 1 was used 15 times
Filter 2 was used 52 times
Filter 3 was used 10 times
Filter 4 was used 33 times
tIME = 7 Jun 1996 17:58:08 +0000
libpng passes test
[localhost:/Library/libpng] miklas% make install
mkdir: /usr/local/include: File exists
make: [install] Fehler 1 (ignoriert)
mkdir: /usr/local/lib: File exists
make: [install] Fehler 1 (ignoriert)
cp png.h /usr/local/include
cp: /usr/local/include/png.h: Permission denied
make: *** [install] Fehler 1
[localhost:/Library/libpng] miklas% sudo mak
make makedbm makemap
[localhost:/Library/libpng] miklas% sudo make install
mkdir: /usr/local/include: File exists
make: [install] Fehler 1 (ignoriert)
mkdir: /usr/local/lib: File exists
make: [install] Fehler 1 (ignoriert)
cp png.h /usr/local/include
cp pngconf.h /usr/local/include
chmod 644 /usr/local/include/png.h
chmod 644 /usr/local/include/pngconf.h
cp libpng.a /usr/local/lib
chmod 644 /usr/local/lib/libpng.a

After the installation i tried to run webalizer getting the following error:

[localhost:] miklas% webalizer
dyld: webalizer can't open library: /usr/local/lib/libpng.2.dylib (No such file or directory, errno = 2)

ls -la /usr/local/lib shows following:

[localhost:/Library/libpng] miklas% ls -la /usr/local/lib/
total 7608
drwxr-xr-x 36 root wheel 1180 Nov 1 20:12 .
drwxr-xr-x 12 root wheel 364 Jul 8 17:27 ..
lrwxr-xr-x 1 root wheel 20 Nov 1 20:12 libcurses.dylib -> libncurses.dylib.5.2
-rwxr-xr-x 1 root wheel 13832 Aug 1 20:12 libdl.dylib
-rw-r--r-- 1 root wheel 122940 Aug 18 19:12 libform.a
lrwxr-xr-x 1 root wheel 15 Nov 1 20:12 libform.dylib -> libform.dylib.5
lrwxr-xr-x 1 root wheel 17 Nov 1 20:12 libform.dylib.5 -> libform.dylib.5.2
-rw-r--r-- 1 root wheel 85368 Aug 18 19:12 libform.dylib.5.2
-rw-r--r-- 1 root wheel 1330912 Oct 20 17:59 libfreetype.a
-rwxr-xr-x 1 root wheel 614 Oct 20 17:59 libfreetype.la
-rw-r--r-- 1 root wheel 179020 Oct 1 03:13 libintl.1.0.1.dylib
lrwxr-xr-x 1 root wheel 19 Nov 1 20:12 libintl.1.dylib -> libintl.1.0.1.dylib
-rw-r--r-- 1 root wheel 243172 Oct 1 03:13 libintl.a
lrwxr-xr-x 1 root wheel 19 Nov 1 20:12 libintl.dylib -> libintl.1.0.1.dylib
-rw-r--r-- 1 root wheel 728 Oct 1 03:13 libintl.la
-rwxr-xr-x 1 root wheel 142696 Sep 2 18:37 libjpeg.62.0.0.dylib
lrwxr-xr-x 1 root wheel 20 Nov 1 20:12 libjpeg.62.dylib -> libjpeg.62.0.0.dylib
-rw-r--r-- 1 root wheel 182476 Sep 2 18:37 libjpeg.a
lrwxr-xr-x 1 root wheel 20 Nov 1 20:12 libjpeg.dylib -> libjpeg.62.0.0.dylib
-rwxr-xr-x 1 root wheel 654 Sep 2 18:37 libjpeg.la
-rw-r--r-- 1 root wheel 67856 Aug 18 19:12 libmenu.a
lrwxr-xr-x 1 root wheel 15 Nov 1 20:12 libmenu.dylib -> libmenu.dylib.5
lrwxr-xr-x 1 root wheel 17 Nov 1 20:12 libmenu.dylib.5 -> libmenu.dylib.5.2
-rw-r--r-- 1 root wheel 44356 Aug 18 19:12 libmenu.dylib.5.2
-rw-r--r-- 1 root wheel 625700 Aug 18 19:11 libncurses.a
lrwxr-xr-x 1 root wheel 18 Nov 1 20:12 libncurses.dylib -> libncurses.dylib.5
lrwxr-xr-x 1 root wheel 20 Nov 1 20:12 libncurses.dylib.5 -> libncurses.dylib.5.2
-rw-r--r-- 1 root wheel 366336 Aug 18 19:11 libncurses.dylib.5.2
-rw-r--r-- 1 root wheel 28436 Aug 18 19:12 libpanel.a
lrwxr-xr-x 1 root wheel 16 Nov 1 20:12 libpanel.dylib -> libpanel.dylib.5
lrwxr-xr-x 1 root wheel 18 Nov 1 20:12 libpanel.dylib.5 -> libpanel.dylib.5.2
-rw-r--r-- 1 root wheel 27028 Aug 18 19:12 libpanel.dylib.5.2
-rw-r--r-- 1 root wheel 206408 Nov 1 20:13 libpng.a
-rw-r--r-- 1 root wheel 73244 Nov 1 20:07 libz.a
-rw-r--r-- 1 root wheel 60558 Jun 25 10:50 strobe.services
lrwxr-xr-x 1 root wheel 17 Nov 1 20:12 terminfo -> ../share/terminfo

--- end ---

Any hints?