According to Jeff Potts from ecmarchitect.com, the developers of the Alfresco Community CMS have pledged to allow contributions from other developers starting with their version 3.0. Potts asked a question about the possibility of the code being opened up at the Alfresco Community Conference a few weeks ago.

Jeff's complete post is here.

Alfresco comes in two flavors: the enterprise-level main product and the free Alfresco Community edition. Both are considered open source projects, but contributions from the general development community have been rare in the past. If it happens as suggested, this could create a network of Alfresco developers similar to that of Drupal and Joomla.