I reinstated my N9 yesterday and got Whatsup working pretty easy by exactly following the procedure that is documented on openrepos.net when you search for whazzappath.
1. Install Wazapp 0.9.22
2. Install wazappath; patches Wazapp for registration problem
3. Open Wazapp and register
4. Quit Wazapp
5. Install Whatsup
6. When open Whatsup, click on button to import from Wazapp.
7. Done

No external PC or browser required; all done from the N9.