Wikipedia suggests it was initially apache, changed to BSL in 2019. https://en.wikipedia.org/wiki/CockroachDB. But still perhaps an example of fairly quick switch to BSL before it had gotten wide market/mind share? I don't know the history.
"We’re adopting an extremely permissive version of the Business Source License (BSL). CockroachDB users can scale CockroachDB to any number of nodes. They can use CockroachDB or embed it in their applications (whether they ship those applications to customers or run them as a service). They can even run it as a service internally. The one and only thing that you cannot do is offer a commercial version of CockroachDB as a service without buying a license."