mulitouch is related to os or device? can n900 have multitouch input method?

its a limitation of the screen. I do not think it is possible via software at this point to have multitouch.

Multitouch is currently only possible on capacitive screens. Basically you trade in precision and pressure sensitivity for multitouch. I'd rather have precision than have to perform awkward gestures with my fingers.
Multitouch is related to the hardware, and then of course to the software to interpret the multiple touch inputs.

this is little bit old, so i think it could eventually be possible :

http://www.youtube.com/watch?v=Bv3X5y-ajtc

if you listen to the video, it has "guidelines" that were given to the touch screen builder. To me this means its a special build and a simple software solution may not be possible. To me, not knowing anything about it, it would seem that there should be a simple software solution out there. I really do not know what the hardware limitation can be. Maybe someone smarter on this subject can give more detail.

I think one of the only places it comes in useful is with zooming. Im sure someone could write something which when one finger goes over the light sensor, the other finger on the screen would zoom.

This would give an impression of multitouch, it has been discussed before.

http://lmgtfy.com/?q=hardware+limita...+touch+screens

take a look at one of the tablets intel showed the other day it as a resistive multi-touch
heres the video it even allows more points of contact than a capacitive screen
http://www.youtube.com/watch?v=iVIKY...os=QKS4KDLfPDE

There isn't any doubt that resistive screens can do multitouch, but it has to be a certain resistive touchscreen that doesnt' exist in the n900 as far as I know.

If its meego its gotta be capacitive.Nokia has made it clear they are concentrating only on capacitive user interface for meego devices (hence no official support for meego onN900).
If you watch carefully at 00:20 he says "..capacitive multi-touch touch screen..."