It doesn't need a plugin to run the JavaFX script, but it takes a plugin to develop JavaFX application!
Careful now. There are two things called "plugin" in this context, and I'm almost certain that Stuart is asking about one (the Java-enabling plugin for web browsers), and you (Rahesh) are talking about the other one (the plugin for NetBeans that helps JavaFX development).
Note that the NetBeans plugin is not required for developing with JavaFX, nor is NetBeans itself (even though you could certainly get that impression from the OpenJFX web site). A regular Java 5 JDK is sufficient.