The main reason I loaded the chdk was to use my S90 for
time lapse/stop motion creation.
Quite surprised that I can't do this.
Anyone know if it's possible?
All CHDK ports support scripting, and they support almost all the same commands. If a specific script doesn't work on your camera, it's up to you to figure out why.
The most common cause of incompatibility would be using hard coded propcase numbers, or making assumptions about the features available on a specific camera.
It's also always possible that a particular port has bugs, and this is more likely in recent ports. If you think you have found a bug, you need to describe in detail what you tried to do, and what the resulting behavior was.