This is the reason given by the Development team of Postnuke for their seperation from PHPNUKE :

You may be wondering why on Earth do we need a fork from PHP-Nuke? There are several reasons behind our insanity. The time is right for a developers version of PHP-Nuke. It wasn't a simple decision, but so far it has been very rewarding.

There were many factors in our decision for forking off. Below are some of the more rational reason, and some of the more irrational ones as well.

1) There is in our opinion a severe need for a more open developement system. This can only speed the direction of the project and help everyone in the end.

2) Ask yourself this. Do you want more features, or do you want more features that work correctly? We feel that in a collective enviroment, we can code very quickly and fix problems that, by ourselves, we might have missed.

3) Did you happen to read: http://phpnuke.org/maxnews.php?ArticleID=1833 This completly soured my outlook on PHP-Nuke. This attitude has become a cancer on the whole community, and frankly I don't much care for the community feel now.

4) How long have we been crying out for a CSS encased version of PHP-Nuke. Well, with Post-Nuke this was our number one priority. There are now no hard coded fonts, or hard coded colors for that matter. The themes themselves have no hard coded colors. It's as simple as changing a few variables at the top of the theme.php, and editing the style.css file, and you have a completly different site.

5) How many bugs have you fixed over various versions, only to see them crop back up in the next version? In an open-developement enviroment, that might be less likely to happen.

6) Has anyone ever sat down and thought, what exactly are core files and what are just the bells and whistles? We are defining the core files, and setting that as our priorities, not adding a haphazard new download.php just before release time.

7) HTML compliance. Yes, the index page for PHP-Nuke validates, but have you ever tried to validate some of the other files? Trust me, it ain't pretty. We have spent considerable time and effort to start to fix these errors. Are they all fixed? Nope. Will they be? Well, if this release is any indication, I would bet you on it.

These amognst other technical reasons are just the tip of the iceburg of why we are forking off.

Now it has been said that an open-developement enviroment will not work because of the egos. Guess what, we have been discussing this for over two months now, and we are still here.

Food for thought.