PBLang is a versatile flat file BBS, requiring only PHP 4.02 support. It has a wide range of user specific settings, various skins/layouts, configurable forums, moderators, email notifications, several levels of restrictions, membership groups, a completely configurable layout, sortable members list, avatars, etc. The emphasis is on configurability and reliability.
PHPX is a Web portal system, blog, Content Management System (CMS), forum, and more. It is designed to allow everyone to be able to have feature-rich, interactive websites even if you do not know a bit of programming. Some key features include fully-integrated forums, downloads, an image gallery with slideshow and auto-thumbnailing, support ticket system, a GUI interface for Web page content management, news with topics and instances, and a whole lot more. It allows you to fully customize the look of your site.
Partyfish is a content managment system with many features, including an information sharing system, commenting system, markup language, built-in BBS, and much more. It is completely themable with a bit of HTML and CSS knowledge. It also has a administration interface, which makes managing the information very easy for the administrators.
PhunkyBB is a Web-based forum system that is distinguished by its use of XSL as its template language. By using XSL, PhunkyBB is able to run on several different platforms, not only in terms of operating system, but also programming language. At this time, it has only been tested and used on PHP, but some test runs have been done on Perl, Python, Tcl, and Ruby.
Pocoo is a bulletin board software (a.k.a. message board). It provides an advanced plugin system with a component architecture which allows other developers to modify Pocoo to their liking without the need to touch existing source code. Because it uses SQLAlchemy, it is possible to use either MySQL, SQLite, Oracle, or Postgres as the storage backend.
PsyPoster Message Board is a small yet robust message board made from scratch in Perl. It was designed to replace Matt's WWWBoard by giving users the look, feel, and functionality they wanted out of a message board. It has scaling support for topics, dynamic pages w/headers and footers, and is secured to prevent misuse.