javassh.org

Java Webstart: Java Webstart [*]

Requires a JVM (1.2 or newer) and webstart (included in JVM 1.4 and later).

As an alternative you could just download the jar and run it like:

$ java -jar jta25.jar

jta25.jar [* (local copy)]
jta25-src.jar [* (local copy)]