Open Architecture Community System (OpenACS) is an advanced Open Source toolkit for developing community web applications licensed under the terms of the GNU GPL.

The Open Architecture Community System provides:

• A large set of applications, that can be used to deploy web sites that are strong on collaboration. Some of the powerful applications are Workflow, CMS, Messaging, Bug/Issue tracker, e-commerce, blogger, chat and forums. OpenACS has dozens more applications.
• A sophisticated application development toolkit, that provides a extensive set of APIs and services to enable quick development of new applications.

Sidenote: OpenACS formerly a product of ArsDigita Corporation (ACS) is one of the more famous products to be based completely on the AOLserver. The ACS code tree forked, with the Tcl code base being maintained by the OpenACS project, while the product line continued at RedHat as RedHat CCM, being re-written in Java / J2EE.

See also:

• http://openacs.org/about/
• Philip Greenspun
• Tcl
• Web_content_management