It’s all there in the license: https://github.com/surrealdb/surrealdb/blob/main/LICENSE. It reverts to Apache-2.0 after four years of the release of a particular version, or on 2026-01-01, whichever comes first.

(This means that if the Change Date is not altered before then, none of SurrealDB will be BSL any more come 2026.)