I think I have to disagree with this. When I got my bike, I too thought it was "stuck". Took the chain off, and tried to kick it over with no luck. It wasn't until I got it into neutral by hand at the front driven sprocket was I able to kick it over.
Just for kicks and giggles, before you do try to free it up, put some ATF/Acetone or PB Blaster in each of the cylinders. A bike that been sitting for long will most likely have some moisture or be very dry so the oil will be good to prevent any damage (even if not stuck).