I don't have access to MacOS, but some general hints:
Correct file permissions don't help if the owner is wrong ...
It looks like there's some confusion about the owner of the Apache-process on MacOS.
The install-guide says its "www", one note say it's "nobody", one note says it's "daemon".
So it's very important to find out the true UID of the running apache2-processes on *your* system.
Here's a hint how to do this:
http://www.dokuwiki.org/install:mac_alt
ps auwx | grep httpd
If you don't get output, replace "http" by "apache".
Check the "ps"-options how to get UID *and* GID !
They are very incompatible.
If they are -edaf your Mac runs AIX or older SunOS ;-)
Here's some other relevant documentation:
http://www.dokuwiki.org/install:permissions
The Unix-section should apply.
Make sure to check directory permissions as well.
Make sure to check not only user but also group permissions.
I see that the MacOS-documentation doesn't mention the group-rights.
Under Linux they are quite important ...