How can I view or start Java Web Start Applications?

Just use javaws as you normally would.

javaws /path/to/your.jnlp

If you want to open in nautilus:

right click on your file -> Open with other application... -> Use custom command -> /usr/bin/javaws

Using the Iced Tea

sudo apt-get install icedtea-netx

Then type

javaws /path/to/your.jnlp

Yep, the finally implemented the option -viewer which enables us to see the cached/installed Java Web Start applications.

They changed this, now this is embedded in the JDK Control Panel which can be launched in unity or in cli using itweb-settings. Go to the cache sidemenu and click on view files.