Disney does still retain all of LA's rights, but those rights never covered the source code, only the game assets (characters, music, etc.). Since this release doesn't include any of the assets, Disney has no say whatsoever over what Activision can and cannot do.
So what if the game sources reference characters and other Star Wars franchise assets directly? The existence of those assets in game happen because of a combination of resources, including images, music, sounds, and references in the sources.
If the rights for the external resource data (textures, images, dialogue, etc) are retained by Disney and that would restrict a source release, I don't see how the source on it's own is any different. The existence of the character or asset in the game is a result of several pieces working together, not just the external data itself. The code provided in this release is very obviously part of the Star Wars universe, I have a hard time believing that Disney or LA has no claim or right over that.
For example, the sources define AI behavior for various enemies that are clearly a part of the Star Wars universe. Why are the images, sounds, and external (e.g. not source) data for these enemies owned by Disney, but not the behavior patterns they exhibit in the game? In the few files I looked at, it wasn't generic AI behavior, it was specifically named and defined based on each enemy type.
I could see someone making the argument that the digital information associated with the characters you encounter in the game are made up of several components and can't be separated from the sources, giving Disney rights over them, just like they supposedly have over the images/sounds/etc.
FWIW I'm not necessarily advocating this position, just trying to wrap my head around how this whole thing works.
It wouldn't surprise me if this goes away. I find it hard to believe that in 24 hours or less they managed to make this happen correctly and legally.
a) A source code on the web can't just go away.
I'm aware of that, I meant it would be removed from SourceForge and no longer an "official" release.
This is an important distinction because it could allow forks to continue development, but if the release wasn't legal in the first place, that wouldn't be possible on a broad scale.