Yes, it's generated from the source, and the tool is proprietary, and Jack has never leaked it out.
I don't blame him, the API docs are one of the great differentiators of Ext. Jack doesn't want any competitors baing able to generate such a great UI for their docs.
Yes. Perhaps he could offer a web service to subscribers where they could pass source code, and out would pop the API for their app. That would be sweet. I'd love to be able to document our huge Javascript client properly.