An interesting quirk about Steamboat Willie is that you still can't put that cartoon up on YouTube or anywhere similar. That depiction of the mouse at the very start, standing at the steering wheel, whistling while spinning the wheel, is still off-limits because the big D put that segment in their into logo for movies, putting it under the protection of Trademark law. Trademark isn't as long-term or wide-scale as Copyright, it only really lasts as long as that Trademark is in common use and for that very specific animation, but they can keep that specific cartoon out of public hands for now. But you can still mess around with that version of MM, just as long as he's not at a ship wheel and whistling.