can i use python instead of java for new Binding development? and what are the advantages and disadvantages
No, all openHAB add-ons must be written in Java.
You do have the option to write rules in Jython but it’s stuck at version 2.7 of Python.
HABApp isn’t a binding nor is it an add-on. It’s a rules engine that runs along side of openHAB and interacts with openHAB through its REST API.