I think it is fair for everyone if Apple wouldn't have contributed back their work on the code as large portion of Webkit itself which under BSD-like license are come from Apple itself.
Just for information, a modern, BSD-like licensed Clang compiler which someday will become a popular replacement for GPL-ed GCC also sponsored by Apple.
Some corporation probably wouldn't have contributed back their work on the code, but some other corporation wouldn't stupid enough to maintain the source code itself which will take a lot of cost. That's why some of them will release their contribution to the base code and collaborate with free software community for the benefit of each. GPL of course not as good as LGPL for this purpose. And this is what BSD community believe in their license for years. (See "Why you should use a BSD style license for your Open Source Project
" for more informations).