A piece of news: a Japanese company (DWANGO) did exactly this and bought the rights for the animation program used by the Studio Ghibli (on Princess Mononoke, Spirited Away and Howl's Moving Castle to name some), Futurama, Balto and Anastasia animators, and released it under the BSD 3-clause license:
https://opentoonz.github.io/e/index.html If such an important program can be bought and freed, then every program can. We should all learn a lesson from DWANGO. (Well, except for the fact that people have become so afraid of the "restrictive" and "viral" GPL license that they will go against their own interest and adopt a permissive license for such an important piece of software, which will inevitably result in it getting a proprietary fork)