Spite does in fact require a tethered boot regardless of whether your exploit is tethered or not. Also, it isn't likely that chpwn will release another version of Spire....seems like development on that has been dead for quite some time now. Maybe he was just waiting for the untether though.
I've been dicking around with trying to get siriport.ru working, but I'm not having much luck in that area. Might be at the point now where we decide whether we want 5.1.1 or Siri, because we can't have both.
I want to try changing my plist file to say I have 5.0.1, install Spire, then change it back....not sure if I am going to shoot myself in the foot that way though.
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I can confirm that changing your plist file and telling it you are on 5.0.1 will allow you to install Spire and it works....however....as soon as you change it back to 5.1.1 it will try to uninstall itself. Now, the big question, does it matter if your plist says 5.1.1?