Surfin' Safari reports that WebKit (the Objective-C API for the Safari renderer), WebCore (the base code) and JavaScriptCore (the base code for the JavaScript implementation) are now open source. With CVS repository and public bug tracking system.
Ultimately, this is of course a fork of khtml and kjs, but by disclosing the sources, everyone can now freely use each other's code and thus the problems between the projects should be off the table for now. Contributions are also to be accepted.