The Collaborative International Dictionary of English v.0.48:

Unreserve \Un`re*serve"\, n.
   Absence of reverse; frankness; freedom of communication. --T.
   Warton.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "unreserve":
   abandon, abandonment, accessibility, approachability, artlessness,
   bluffness, bluntness, broadness, brusqueness, candidness, candor,
   communicativeness, conversableness, directness, extroversion,
   forthrightness, frankness, freedom, freeness, genuineness,
   immoderacy, incontinence, indiscipline, ingenuousness,
   intemperance, irrepressibility, laxness, licentiousness,
   noncoercion, nonintimidation, openheartedness, openness,
   outgoingness, outspokenness, permissiveness, plain dealing,
   plain speaking, plainness, plainspokenness, riotousness, roundness,
   sincerity, sociability, straightforwardness, talkativeness,
   unconstraint, uncontrol, uninhibitedness, unrepression,
   unreservedness, unrestraint, unrestriction, unreticence,
   unruliness, unsecretiveness, unstrictness, unsuppression,
   untaciturnity, wantonness, wildness