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.

All Java Web Start applications launched later use the same Java Web Start client. When the user clicks on the URL in the browser, the server serves a JNLP file to the client.

Like Java applets, your application will be constrained to a sandbox on the client unless you used signed jars and configure permissions correctly in your application's JNLP file.