>This is not the official contract tracing app (that one can be found here https://github.com/corona-warn-app)

This sounds like they do the same thing. But the luca app is for check-ins ( which are mostly still done with pen in paper in germany ). Check-ins are not supported by the official corona-warn-app (yet).

Also 2 states already purchased the app and 8 other announced to purchase it [1]. So if you live in one of these 10 states (out of 16) then you can consider the luca app to be official.

[1] (German) https://www.heise.de/hintergrund/Corona-Apps-Die-wichtigsten...