Actually OSX can open files with the default app with command "open"...
|open /path/to/file.html( | [shell]
if you need some specific browser (like Plainview, for example) that is not the default one you should use something like:
|open /path/to/file.html -a Plainview.app( | [shell]
If you want to run only the .jar, you may prefer to run
|java -jar applet.jar( | [shell]
josé