The first client library is now released · 9 August 2006 by Crosbie Fitch
Version 0.1 of the PHP5 source code (GPL v2) to the first release of a client library for the Contingency Market is downloadable here: CM_PHP_Client_v0.1.zip
By way of simple demonstration it is hosted here
At the moment library classes have only been implemented to handle sessions and agents. Events, contingencies, offers, and deals will be implemented in due course.