It may look similar, but the A490 is one of the 2010-released cameras. Until a couple of weeks ago it was not possible to produce a firmware dump for any of the 2010 cameras - such a dump is a necessary first step in porting CHDK to a camera.
A new dumper has now been written and I think a dump of the A490 has been produced, but this is just the first step. Now someone who has the camera AND the time and skill to do the porting has to do the work. That could take some time (weeks probably, maybe months).