Firefox uses a complete GRE which includes all parts that a Thunderbird GRE includes.
Their XULRunner based GREs are identical.
So the Mozilla browser and mail program only have a different GUI!
K-Meleon uses a selected subset that ideally only includes Mozilla GRE parts that a web browser needs.
Your screeshot shows part of Firefox's XUL based GUI
K-Meleon does not use that XUL technology for its GUI.
So IMHO Your chances of porting webmail notifier are not good.
You could try to get the Opera or Chrome versions of that application working.
p.s. Your cahnces may become better in case K-Meleon would change to use the full Xulrunner GRE. Few here do like that option.
Edited 1 time(s). Last edit at 10/03/2011 11:55PM by guenter.