It looks like Google owns the project and that, to contribute, you have to turn over copyrights [0]. I think the ownership makes it "by Google" more than employing the main dev.
[0] - https://cue.googlesource.com/cue/+/HEAD/doc/contribute.md#st...
[0] - https://cue.googlesource.com/cue/+/HEAD/doc/contribute.md#st...
The latter is lower friction, in my opinion.
This is especially common for "personal" projects that people end up working on or using on the clock.
I don't know if this was the case with Cue specifically (this is the first I've heard of the project, but less boilerplate in my JSON has some appeal).
*grant a copyright license