In a recent conversation with the developers of RuneScape (Jagex), the issue came up that while the JRE/JDK installer will associate Java Web Start with JNLP files, it doesn't (at least on Linux) automatically update the user's prefs.js or similar, so that they continue to get a dialog box asking whether they want to launch the file with JWS or save it to disk each time they click a JNLP file. From an internal discussion it sounds like we do this on Windows; we should do the same on our supported Unix platforms.