The Collaborative International Dictionary of English v.0.48:

Originative \O*rig"i*na*tive\, a.
   Having power, or tending, to originate, or bring into
   existence; originating. --H. Bushnell. --
   O*rig"i*na*tive*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

originative
    adj 1: having the ability or power to create; "a creative
           imagination" [syn: creative, originative] [ant:
           uncreative]
    2: containing seeds of later development; "seminal ideas of one
       discipline can influence the growth of another" [syn:
       germinal, originative, seminal]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "originative":
   behind the scenes, causal, causative, conceptive, conceptual,
   constitutive, constructive, creative, decisive, demiurgic,
   determinative, effectual, esemplastic, etiological, fecund,
   fertile, formative, generative, germinal, ideational, ideative,
   imaginative, ingenious, innovational, innovative, inspired,
   institutive, inventive, notional, occasional, original, pivotal,
   pregnant, productive, prolific, seminal, shaping, teeming,
   visioned