From twitter (Max from Quarkus):
https://twitter.com/maxandersen/status/1527566739562700802

Richard Fontana says there is no point in having copyright notices for every single file, so Quarkus doesn't have any there. The repo root info suffices (DRY).
https://github.com/quarkusio/quarkus/discussions/25592#discussioncomment-2761898

Copyright notices cause extra merge changes, but more importantly they are a pain (creating FUD) for quickstart users (they want to remove them in their clone but feel like they can't).

Apply the Quarkus approach to optaplanner-quickstarts, optaplanner and optaweb-*.