Installing Wazapp developer versions from Github howto:

requirements:

1. latest official Wazapp installed ( http://wazapp.im/ )
2. Filebox installed ( http://store.ovi.com/content/204982/download )
3. N9 QTweak installed and hack H activated ( http://talk.maemo.org/showthread.php?t=80600 )

steps:

1. quit Wazapp from within the app (menu -> quit)
2. delete /home/user/.wazapp/*.db file (using Filebox or term)
3. download latest dev .zip from wazapp github ( https://github.com/tgalal/wazapp/zipball/dev )
4. extract .zip on Your pc
5. now zip only /client folder with all subfolders & structure
6. delete wazapp & wazapp_init files from that zip
7. transfer it to Your N9
8. open rooted Filebox (password: rootme) and move that .zip to /opt/waxmppplugin/bin/wazapp folder
9. extract .zip in that folder accepting to overwrite all existing files
10. open terminal, enter devel-su, then rootme as the password
11. execute command: apt-get install python-dateutil (then wait)
12. execute: cd /opt/waxmppplugin/bin/wazapp
13. execute: chmod 755 *
14. exit terminal
15. start Wazapp from Your homescreen
(16. if Wazapp doesn't start -> reboot + step 15)

p.s.: deleting that .db file in step 2 means deleting Your chat history, so bear that in mind

(Thanks to @TMavica and @knobtviker)