That's wrong. Dan created Redux while he was actually unemployed. I'd have to check the exact timeline, but I believe he left Stampsy in late 2014 or early 2015, and was actually getting some funding from an OSS collective-type thing while he developed Redux in preparation for React Europe.
Redux was developed in June/July 2015, and demoed at React Europe on July 5, 2015 [0].
Redux 1.0 was released on Aug 14, 2015 [1].
Per the tweet linked from that page [2], Dan didn't join Facebook until November 2015, well after Redux had been released.
So, he most definitely was _not_ working at FB when he developed Redux.
[0] https://www.youtube.com/watch?v=xsSnOQynTHs
[1] https://github.com/reduxjs/redux/releases/tag/v1.0.0
[2] https://twitter.com/dan_abramov/status/671135846830075904
The source I have says that Dan Abramov created Redux while working at Facebook on React[0]. So while Redux has never been under the official governance of FB, it was created by FB employees for a FB project (React) while in parallel working on that project.
[0] https://golden.com/wiki/Dan_Abramov_(software_engineer)-99B8...