Java in the browser ("Java Applets") have been deprecated since at least 2009, and since at leastlatest 2017, no browser supports them anymore (and that's not something that was disabled. The interfaces for these are just gone.).
So, whatever this is, if it relies on Java in the browser, it's dead as a doornail.
However, my suspicion is that your PDF is simply obsolete, as the official website (allstarlink.org), which is the only authorative resource, I'd say, makes absolutely no mention of it.
So, your problem is that you've got a website and it doesn't work. I'm afraid nobody can really help you but the administrator of the server you're connecting to.