Childs is named as Umbrel's co-founder in the announcement his co-founder posted to the project's community forum on 29 October 2021, which points readers to a longer account of "how @lukechilds and I met, why we started Umbrel, our journey so far, and what lies ahead".
His public work is in the repositories. Umbrel is developed in the open at github.com/getumbrel, and umbrelOS is published under the PolyForm Noncommercial 1.0.0 licence, which permits use, forking, modification and redistribution for personal and nonprofit purposes and requires a separate arrangement for commercial use.
Nothing else about him is asserted here. The directory records the role he has publicly taken and the code that carries his name, and leaves the rest alone.