According this little bit I found on Io9 the other day John Connor is the Voice of the Resistance.

In order to be creative and pique interest for Terminator Salvation I’ve chosen to do small VoTR communications.

Here is the first one. (Please excuse it’s ghettoness I have no leet after editing skill nor proprams) oh and max your sound…I always have mine maxed.

John Connor’s message to The Resistance