There's a trick for downgrading if you're on Mac:
sudo rm -fr /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
then you can install the earlier version.
Since you were kind enough to update the viewer, I went ahead and brought it back to version 8 build 20 to test - I can confirm it...
hmmm, there was no Java when it booted into 10.9.4 so I followed the links and downloaded JRE 8 build 20. Now the JAR quits with a message "the Java JAR file count not be launched". It tells me to check the console, but I don't see anything there.
First: A big thank you for this. I spent a bunch of time trying to hack my way through the HTML files trying to make something work, but this was exactly what I wanted.
A question: I'm running it now under Mac OS X 10.8.5. I'd like to upgrade to the newest 10.9.x release, but I want to make...