OpenCyc is the open source version of the Cyc(r) technology, the world's largest and most complete general knowledge base and reasoning engine. A new release with even more content, better performance, and improved reliability will be up shortly.
This is one approach to implementing the ideas discussed as the Public Domain Knowledge Base.
Originally coded by Stephen Reed before joining Cycorp and currently maintained by Vic Bancroft. The next release with contributions made here will be versio