> never gave back anything

Apart from Clang/LLVM and WebKit you mean?

Ok in fairness the LGPL license of KHTML was a huge reason the WebKit source was available (for ages it was just reluctant tarball dumps) but I don't think that's the case for LLVM.

I don't think the GPL has really meant corporation's have given back significantly to Linux. There are still plenty of closed source drivers. The main motivation to give back is the extremely high cost of maintaining out-of-tree modifications (e.g. Android's binder).