Hydra Columnar is a fork from Citus Columnar c. April, 2022.
Citus: https://github.com/citusdata/citus
BTW, Citus license is GNU Affero General Public License (github lists “conditions: same license”) and hydra is Apache. How is that possible if the latter is a fork? There’s probably something about these licenses I’m not aware of and I’m curious.