You might argue that in a court of law you could get away with violating their intent because the license they chose does not clearly represent it.
Absolutely. That's why companies spend millions on license creation. Intent only matters if text of the license itself have no clear legal meaning. Otherwise why bother with all these expenses if owner can change rules at any time by publishing new interpretation of the license? You can give additional permissions at any time (it effect you are just creating brand new license which does not affect anyone who does not use your newfound generosity), but additional restrictions... that's entirely different thing. And the ability to actually install new library on the target system is most definitely new restriction (from the POV of distributor, not from POV of end user!).
I don't know if that is a valid legal argument or not, especially considering that they have made their intent clear.
It really depends on many things. They have not even added this explanation to the downloadable package, they have not made any movements to make sure potential user will actually see (let alone agree) to this novel interpretation, etc. Hard to see this tightening of the license valid. It may even be considered extortion in some jurisdictions if the other side will prove that it got the software before the appropriate entry in FAQ was added.
But it is not morally valid.
Moral is in eyes of the beholder. It differs from person to person and from society to society. That's why we need all the laws, treatises and licenses: to decide what to do when two persons claim opposite things yet both feel they are right.
Iff WebKit is only licensed under LGPL, I don't see how Apple satisfies the requirements for re-linking even nominally.
It does not. Why should it? Re-linking requirements is just one option. There are others. For example 2b:
Use a suitable shared library mechanism for linking with the Library. A suitable mechanism is one that (1) uses at run time a copy of the library already present on the user's computer system, rather than copying library functions into the executable, and (2) will operate properly with a modified version of the library, if the user installs one, as long as the modified version is interface-compatible with the version that the work was made with.
Note how this requirements says literally nothing about your ability to actually put this library on the user's computer system, it just dictates that if library is somehow found a way there then it must be used.
And yes, WebKit is most definitely available only under LGPL (see Wikipedia for the explanation WRT why). Apple is not sole copyright holder by far.
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