Resolution:
For Rendezvous 5.x:

You can use the Java API on this platform, but you must use it through the Rendezvous Agent. The JNI layer of Rendezvous has not been ported, thus this limitation.

To do so, you can FTP "rvj.jar" from a non-AS/400 system to the 400's IFS. You will have to extract the jar file and recreate it, since the AS/400's Java environment cannot handle the jar files as shipped.

For Rendezvous 6.x:

a) For Rendezvous 6.0 -> 6.4:

You can FTP "tibrvj.jar" from a non-AS/400 system to the 400's IFS. You will have to extract the jar file and recreate it, since the AS/400's Java environment cannot handle the jar files as shipped.

b) For Rendezvous 6.5 and later versions of Rendezvous 6.x:

The JNI layer of Rendezvous has been ported.
You can use the Rendezvous API for Java on the AS/400 as on any other platform.

For Rendezvous 7.x:

The JNI layer of Rendezvous has been ported.
You can use the Rendezvous API for Java on the AS/400 as on any other platform.