The Collaborative International Dictionary of English v.0.48:

Gladful \Glad"ful\, a.
   Full of gladness; joyful; glad. [R.] -- Glad"ful*ness, n.
   [R.] --Spenser.
   [1913 Webster]

         It followed him with gladful glee.       --Spenser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gladfulness
    n 1: experiencing joy and pleasure [syn: gladness,
         gladfulness, gladsomeness]