A licence is one customer's entitlement to a Marketplace app — their tier, hosting (cloud or server/data-center), status (active, cancelled, …), trial flag, ARR, partner, and maintenance window. It is keyed by an entitlement number, which is the natural key the sync reconciles against.
Each sync fetches the current licences from Atlassian and upserts them: first_seen_at is preserved, last_seen_at advances, and the diff between the previous snapshot and the new one is what the synthesiser turns into lifecycle events (trial started, converted, renewed, churned, …).
So a licence row is a current profile, not a history — the history lives in the events synthesised from how that profile changed over time.