Is 9iAS necessary for Web-enabled database applications?

Most of our Web applications were developed using MOD PL/SQL and/or PSP and some Java. We are using 9iAS to support these applications, but we are using it only to create DAD for our Web-enabled database applications. Do I actually need 9iAS or just an Oracle HTTP server (which comes anyway on the 9i database installation)?
No you do not need the entire application server and yes you could implement the PL/SQL application on the database's OHS. As to the Java it really depends on if the Java can be loaded and execute inside the Oracle database. If you implement J2EE you will need the Oracle Container for Java (OC4J). If all you have are some serves or Java that can execute in the database, then you can use the OHS that comes with the database.