Since JNLP files are simply Java Web Start files that open applications through an Internet browser, any browser that works in Windows 8.1 will open a JNLP file as long as you have Java installed.

Applications launched through Web Start will find that many methods that worked fine directly atop the Java virtual machine will fail with SecurityExceptions inside the Web Start imposed sandbox.

Java Web Start simplifies deployment of applications, but Sun's Plug-in makes the task even easier. See how the Java Plug-in from Sun enables browsers to fetch a Java Virtual Machine (JVM).