The Collaborative International Dictionary of English v.0.48:

Unforced \Unforced\
   See forced.

WordNet (r) 3.0 (2006):

unforced
    adj 1: not brought about by coercion or force; "the confession
           was uncoerced" [syn: uncoerced, unforced, willing]
    2: not resulting from undue effort; not forced; "a voice with a
       pleasingly unforced quality"; "his playing is facile and
       unstrained" [syn: unforced, unstrained]

Moby Thesaurus II by Grady Ward, 1.0:

84 Moby Thesaurus words for "unforced":
   a beneplacito, a discretion, abandoned, ad arbitrium, ad lib,
   ad libitum, al piacere, arbitrary, at choice, at pleasure, at will,
   autonomous, deliberate, discretional, discretionary, elective,
   free, free will, go-go, gratuitous, immoderate, incontinent,
   independent, indulgent, intemperate, intentional, irrepressible,
   lax, licentious, loose, nonmandatory, nonrestrictive, offered,
   optional, out of control, out of hand, permissive, reinless,
   riotous, self-acting, self-active, self-determined,
   self-determining, spontaneous, unasked, unbesought, unbidden,
   unbridled, uncalled-for, unchecked, uncoerced, uncompelled,
   unconstrained, uncontrolled, uncurbed, ungoverned, uninfluenced,
   uninhibited, uninvited, unmastered, unmeasured, unmuzzled,
   unpressured, unprompted, unreined, unrepressed, unrequested,
   unrequired, unreserved, unrestrained, unrestrictive, unruly,
   unsolicited, unsought, unsubdued, unsuppressed, voluntary,
   volunteer, wanton, wild, willful, willing, without coercion,
   witting