The fact of the matter is that the editor is and has been open source, and no one has taken the time to ensure that it will fully load with and/or create a port of it to Mono. And I would honestly be surprised if anyone seriously wants to try and develop a video game on their iPad. That doesn't even make sense.
The majority of users are running Windows to develop their games. Even if official editors were available for Mac and Linux, it wouldn't create a huge influx of change in this statistic, as there are alternatives already available (emulation, etc.).
If you would read the context of what RickJ (and others) have said, none of us have any specific allegiance to the CHM format, but rather simply to the benefits that it offers. Alternatives with similar features are available, as has been pointed out, and the whole topic is under review. Otherwise this thread wouldn't even exist.
Just because a program isn't updated every six months doesn't mean it automatically becomes unusable. AGS is not going to die, and I for one would really appreciate if you would stop your filthy fear mongering.