So Pe

SOPE

An OpenSource alternative to WebObjects which contains various extensions to WebObjects in the spirit of Zope, including support for XML-RPC or WebDav.

Widely known as the application server basis for OpenGroupware, a huge OpenSource web application consisting of about 300 reusable WebComponents? and various applications based on the SOPE server. 7-8 years into development, SOPE is extremely mature and well optimized.

SOPE:X, a part of SOPE, has advanced support for the MacOsx platform and development tools (like WebObjectsBuilder? and ExCode).

http://www.opengroupware.org/en/devs/sope/