As I understood from chdk wiki the script can run any bin files not for boot only.
Yes, but this http://chdk.wikia.com/wiki/Canon_Basic/Scripts/Loader script was meant to reboot the camera with a loaded binary, it was not meant to return normally. Of course you can create a proper event procedure that can also return, but then you don't need reboot.
If someone wrote an FLT loader for canon basic, that could be quite useful.