The Collaborative International Dictionary of English v.0.48:

Unmonopolize \Un`mo*nop"o*lize\, v. t. [1st pref. un- +
   monopolize.]
   To recover or release from the state of being monopolized.
   [R.]
   [1913 Webster]

         Unmonopolizing the rewards of learning and industry.
                                                  --Milton.
   [1913 Webster]