The Sun JavaTM System Application Server Platform Edition 9.0 Update 1 product is a Java EE 5 platform-compatible server for the development and deployment of Java EE applications and Java Web Services. Production use of this server is free of charge. Sun Java System Application Server Platform Edition is free for development, deployment and redistribution. Customers interested in redistribution should contact Sun OEM sales for a redistribution license.
As for Update 1, well, that's the fixpack/update that comes between the release of the product, and the second update.