You could always use the JDBC driver jt400.jar
It is available from http://sourceforge.net/projects/jt400
You will need to download the JTOpen-full package and extract the jt400.jar file to the proper folder.
I just made a connection with it yesterday to connect a SQL 2000 server and it works fine. Not sure your application or whether it meets your needs.
Class Name: com.ibm.as400.access.AS400JDBCDriver
URL: jdbc:as400://RDB Name/Schema
You can find more on the connection string at http://publib/boulder.ibm.com/infocenter/iseries/v5r3/index.jsp
Search for AS400JDBCDRIVER