Must be signed.

This is the difference between ActiveX and Javaapplect.
An ActiveX download, run multiple times, and run with no difference to the application, can get a wide variety of resources, manipulate files, memory, and other resources, so potentially devastating.
While the Java Applect must be downloaded before running, and the JVM left a small controllable place for the applet to perform, its available resources are limited and controllable. So there's no need for signatures or anything. That can be run.
In view of this, Microsoft provides a digital signature mechanism for ActiveX. In fact, digital signature does not prove that this thing is destructive, but only to prove that this thing is written by WHO. In this way, if there is a problem, someone will be responsible. This is the whole mechanism of digital signature.
It's like you hired a nanny from the outside to pick up things at home, you can't supervise at home every day, so you have to find a reputable nanny intermediary to help prove that the nanny has no bad habits (such as the habit of sticking needles), will not steal your money, even if you steal, you can find it through intermediary agencies. ActiveX is equivalent to this nanny.
And Applect is sort of like an hourly worker. You don't give him your keys, he comes to work, you're right next to the supervisor (when it's different from the hourly work, the applet does not meet with the money or the color of the whim to do any irresponsible action on you).