Probably the best option (since DB2 is already running where your app is) is to configure a connection to the remote DB using the DB2 control center or cmd line processor. Then configure a DataSource in WebSphere using COM.ibm.db2.jdbc.DB2ConnectionPoolDataSource as the implementation class. When you install the driver, put db2java.zip in the classpath.
You can use the net driver, but you will need the DB2 applet server server running on the db server. The net driver is type 3.
You could also purchase a type 4 driver from someone like hit software (http://www.hitsw.com
) and connect directly to your remote db).