NetX provides a drop-in replacement for javaws (Java Web Start). Since upstream NetX is dead, the IcedTea Web project is hosting a fork of the original code. However, as icedtea-web has evolved to complex set of tools, extensions and tests, it has now only a few lines of code shared with the original implementation.
Tool to open and view .jnlp files.
sudo apt-get install icedtea-netx