Apache resigns from the Java Community Process executive committee

Your argument seems confused to me. TCK doesn't decide whether a implementation is free or not. Apache is free to continue developing harmony and it will remain under a free software license. Apache's issue must be that they cannot call their implementation Java and whether one can call something by some particular name has nothing whatsoever to do with whether or not a GPL'ed implementation exists. I don't see the connection. A GPL'ed implementation can only guarantee certain rights in terms of copyright licensing and to some extend patent rights assuming you use the same exact implementation. You can still be sued for a independent reimplementation. You can still be sued for trademark violation and so on.

As to the question of whether GPL can be revoked, it is sufficiently answered by looking at how many vendors are exercises GPL rights and have huge legal departments. If they have convinced themselves that it is not a risk worth worrying about, I don't see why I should be concerned about supposedly implicit admission on a link you cannot find. It seems too flimsy. I will let an actual court case decide on it. Until, the burden of proof exists on the side making that claim.