The Collaborative International Dictionary of English v.0.48:

Unfetter \Un*fet"ter\, v. t. [1st pref. un- + fetter.]
   To loose from fetters or from restraint; to unchain; to
   unshackle; to liberate; as, to unfetter the mind.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "unfetter":
   cast off, detach, disengage, doff, free, liberate, loose, loosen,
   release, remove, take off, unbar, unbind, unbolt, unbridle,
   unbuckle, unbutton, uncage, unchain, unclasp, undo, unfasten,
   ungag, unglue, unhandcuff, unhobble, unlace, unlash, unlatch,
   unleash, unlock, unloose, unloosen, unmanacle, unmuzzle, unpen,
   unpinion, unshackle, unstick, unstrap, untether, untie, untruss,
   unyoke, weigh anchor