The Collaborative International Dictionary of English v.0.48:

Dependant \De*pend"ant\, Dependance \De*pend"ance\, n.,
Dependancy \De*pend"an*cy\, n.
   See Dependent, Dependence, Dependency.
   [1913 Webster]

   Note: The forms dependant, dependance, dependancy are from
         the French; the forms dependent, etc., are from the
         Latin. Some authorities give preference to the form
         dependant when the word is a noun, thus distinguishing
         it from the adjective, usually written dependent.
         [1913 Webster]

WordNet (r) 3.0 (2006):

dependance
    n 1: being abnormally tolerant to and dependent on something
         that is psychologically or physically habit-forming
         (especially alcohol or narcotic drugs) [syn: addiction,
         dependence, dependance, dependency, habituation]
    2: the state of relying on or being controlled by someone or
       something else [syn: dependence, dependance,
       dependency]