The song is public domain, composed in the late 19th century based on a poem by Goethe.

How are they 'stealing' it? They have flooded YouTube with fake piano video playings of a different song titled "Der Zauberlehrling".

Ultimately, they would seek royalties whenever the actual song is played sometime in the future when Fantasia is rereleased.

This is easily a $15 million USD steal. Quite a nice retirement package for only having to pay 20 people to play the wrong song and erase it from history.