http://www.kimballcastle.com/index.html
This link has not been updated since 2007. From the article written on the castle, the town of Gilford is the current owner. The AG office has been after the town to do something.
This link gives you an idea how bad the castle is and from the looks of it, The town might as well give the castle away!
http://www.dupontcastle.com/castles/kimball.htm
I also recall that SyFy's "Ghost Hunters" were seeking permission to explore the castle.