WebCore and JavaScriptCore are primarily written in C++ and all code within them is virally licensed under LGPL. Apple did not change the license. Some portions of WebCore and JavaScriptCore if compiled independently would be licensed under BSD. WebKit is a thin shell over the above-mentioned two. On OSX WebKit's primarily implemented in Obj. C. On Windows it's primarily implemented in COM/C++. WebKit if compiled independently would have a BSD license but when compiled with WebCore and JavaScriptCore has an LGPL license virally.
So, the combo WebKit with WebCore and JavascriptCore is LGPL, not BSD.
The only reason to contribute to a BSD project is when you dominate the segment, like Apple does with WebKit browsers, and you want more companies to feed around your ecosystem increasing its value for you.
Don't assume Steve Jobs does it out of his good heart. The OPENSTEP OS was one of the more closed (as in "doesn't play well with others") Unix variants of its time.
