Can a module copied into a JAR archive be considered a startup component?

No, a module simply copied into a JAR archive is not considered a startup component.

A startup component in Java is usually a class with a public static void main(String[] args) method, which is specified in the JAR manifest via the Main-Class attribute. Without this specification, the JVM does not know which class to launch at application start.

Example of a manifest for launching:

Main-Class: com.example.MainApp

Thus, for a module to become a startup component, you need to define the main class and specify it in the JAR manifest.