wuts the difference between the two?? n wuts phpbbhacks....is that only to build yourself a forums page?

Both php-nuke and postnuke are content management systems abbreviated as cms. Both have many good features. In fact, postnuke is a fork of php-nuke, meaning they came out from php-nuke and develop another cms. Therefore, you may find similarities, but when you start using you will find the difference too.

Copyrights of php-nuke and postnuke:
In php-nuke you cannot remove the footer copyright unless you pay ($10 US). However, in postnuke you can remove the footer copyright but meta tag copyright must remain so that if the source code of the site is viewed it will be visible.

phpbbhacks has many cool addons and templates of pbpbb forums. It is not exactly a cms, it is only the hack site of phpbb forum.

If you want to build only a forum site you can use phpbb at phpbb.com or simplemachine forum at simplemachine.org

But php-nuke and postnuke will help you build content rich websites not just forum. Forums must be installed in both the nukes, it doesn't come with the original package. You must download separeately from their respective sites. Though both uses phpBB forums but a little bit of modification is required which is done by both the nukes. Find more from their respective websites.

I hope this helps.