Working with cameras all day, yes.. it's quite possible. There are about 80 different knobs and tuning parameters on CCD chips these days, and the controllers that operate them can have literally hundreds, depending on how complex they are. Given the N900 has integrated optics, amplification, and compression bits... I'd be very surprised if the raws from two different apps without identical shared camera/chip setup code got the same raw from a single CCD. Not to mention things like drift and noise, which will change from shot to shot in the same app.