> Can extend itself as it runs. For example Wordpress, running off of php files can download plugins to its own server (which are just more php files) to instantly extend itself. Without restarting or redeployment. (What other web platforms can do this?)

Java: Use a classloader to load a JAR and instantiate one of its classes: https://stackoverflow.com/questions/60764/how-should-i-load-...

.Net - use an AppDomain (or other methods): https://stackoverflow.com/questions/1137781/correct-way-to-l...