I don't know the exact dates, but Facebook turned osquery over to the community back in 2019 or 2020, after a period of uncertainly over (reasonable!) conflicting development interests[1]. It became a LF hosted project sometime after that.

(I don't know whether they still use it in-house.)

[1]: https://blog.trailofbits.com/2019/04/18/announcing-the-commu...