The original XULRunner and ChatZilla plan was to wait until the 1.9 version of XULRunner was officially distributed - 1.8 was never going to have the necessary shared UI or support - and then produce a ChatZilla package that works on it. Ideally, we would use the same XPI as for Firefox, SeaMonkey, etc. installs, although there were/are still some pretty critical hurdles to overcome for that to work. Even if it was a separate XPI, it would be a normally-size ChatZilla XPI, and could be on Firefox Add-ons.
So much for that.
After getting over the initial "WTF?" reaction, we need to decide on the way forward for ChatZilla on XULRunner. Thanks to tH's wonderful ChatZilla on XULRunner page (which include mozilla.org built nightlies from the appropriate dates), we do actually have a measurable percentage of our user base running this configuration. A small percentage, but not zero.
- Do we build XULRunner ourselves? This would require a lot of effort on our part, and really should be shared with other projects if possible.
- Do we only make available our ChatZilla package, and tell users to find their own XULRunner (or link to someone else who is making them)?
- Do we give up trying to support XULRunner entirely?
Right now, I don't know, but the last option is looking disappointingly good.