…claims that in the fine print of the Java 9 note is a statement saying the Java Deployment Technologies are deprecated, specifically mentioning "WebStart" and "JNLP" being deprecated along with the Applet API & Java plug-in. The source is this page listing deprecated parts of Java 9:
Java Deployment Technologies are deprecated and will be removed in a future release Java Applet and WebStart functionality, including the Applet API, The Java plug-in, the Java Applet Viewer, JNLP and Java Web Start including the javaws tool are all deprecated in JDK 9 and will be removed in a future release.
JDK-8184998 (not public)
This is surprising news to me. While the Applet deprecation has been well publicized, Java Web Start & JNLP has always been offered as a well-supported alternative.