1. download and install X11 server from Apple:
http://www.apple.com/downloads/macosx/apple/x11formacosx.html

2. download & install PD :
http://prdownloads.sourceforge.net/pure-data/PureDataInstaller_0.37-2003.10.02.dmg?download

3. install the present package ( http://tdegoyon.free.fr/pdp_pidip_osx.tar.gz )
in / :

sudo cd <where you downloaded pdp/pidip>
sudo cp pdp_pidip_osx.tar.gz /
sudo cd /
sudo tar xvfz pdp_pidip_osx.tar.gz

4. install the fonts on your system :

sudo mkdir /usr/X11R6/lib/X11/fonts/TTF
sudo cp /usr/local/lib/pd/pdp_pidip_osx/fonts/* /usr/X11R6/lib/X11/fonts/TTF

5. create a .pdrc file in your home directory with a text editor containing the following lines :

-rt 
-path /usr/local/lib/pd/extra:/usr/local/lib/pd/pdp_pidip_osx/abstractions 
-lib /usr/local/lib/pd/pdp_pidip_osx/pdp

7. launch the xfree server with the X server icon you have in your toolbar

8. launch pd from the icon : 

you should see the following information when starting pd :
PDP: pure data packet
PDP: version 0.12.1
PiDiP : additional video processing objects for PDP : version 0.12.13 ( ydegoyon@free.fr )

IMPORTANT : use pdp_ieee1394 for video capture ( instead of pdp_v4l on linux ) 
and pdp_glx for video output ( instead of pdp_xv on linux )