Samsung made the kernel source for the international Galaxy S III available just a few days of releasing it to the masses. It is currently available to download via Samsung’s Open source Portal for developers who wish to work on custom ROMs for the handset. However if you are a regular user, there isn’t much you can do with it.
While we are all waiting to see the US variants of the Galaxy S III, folks who have purchased the unlocked version will be able to have first dibs at the all the upcoming custom ROMs such as CyanogenMod. If you’re a developer, the link to the kernel source is below.