Mike Benoit <ipso@snappymail.ca>
    Wrote initial "proof of concept" implementation, and maintains documentation & code base.

Dan Cech <dcech@phpwerx.net>
    Implemented the MPTT code, '_group_' feature, and ACL checks in the test suite.
    
Gordon Luk <gluk@dfafunds.com>
    Native ACL_Check module for Perl, and wrote comments for phpDocumentor.

Ben Margolin <ben@prince.org>
    Caught and fixed several bugs.

R. Kunoth <R.Kunoth@web.de>
    Caught and fixed several bugs. 
    
Karsten Dambekalns <k.dambekalns@fishfarm.de>
    Sent in several patches to fix PHP warnings, and helped with the documentation.     
    
Martino Piccinato <martino@nexus.it>
    Modified several API functions to help keep data in sync across tables.    
    
Paul Munn <pmunn@munn.com>
    Sent in Postgres7 table schema, plus some very good suggestions. As well helped with the documentation. 

Fred Cohen <quadra@demosoft.org>
    Sent in Oracle 8i table schema. 
    
Eric Batchelor
    Always there to bounce ideas off of, he has consistently helped me out in many areas, including testing.

Monte Ohrt <monte@ispi.net>
Andrei Zmievski <andrei@php.net>
    Together they made the best template engine available for PHP. Awesome job. 

John Lim <jlim@natsoft.com.my>
    Author of ADODB, also the best database abstraction layer for PHP. 

Rasmus Lerdorf <rasmus@php.net>
    For starting what eventually became the coolest programming language ever.