This page soliciting donations to help rebuild the castle includes the following English explanation:

— start quote — All donators will receive an e-book of Kumamoto Castle Special Edition, of weekly “Japan Castle”, published by DeAGOSTINI. (The e-book is only in Japanese.) Kumamoto Castle is one of the three most magnificent castles in Japan. It was constructed on the order of Kiyomasa Kato in 1607. This truly grand and magnificent castle was seriously damaged by the massive earthquakes in April, and now needs your help for its reconstruction. This fund raising will give you an opportunity to express your support for the castle. Thank you for your kind and warm support. — end quote —

http://donation.yahoo.co.jp/detail/5064001/