"While 64-bit Java software is not yet offered on HP-UX or Sun Solaris, we will be offering a free download of our AIX developer kit, Java 2 Technology Edition, Version 1.3.0 for AIX 5L, in early ...

Developers should download the JDK package (Java Development Kit) and non-developers should get the JRE (Java Runtime Environment) package. You don't need both.