I can imagine a few reasons why they'd do this, but some of it may just be 'why not'. Studio Ghibli has done the same thing with their animation software and it hasn't turned into a disaster for them. Making movies, especially movies that people will pay to watch is hard, and any serious competitors already have their own solutions. If people use moonray and that becomes a popular approach, competitors who don't use it are at a disadvantage from a hiring perspective. Also, DreamWorks controls the main repo of what may become a popular piece of tooling. There's soft power to be had there.