Not yet. When we built the site, Payload's licensing and business model was built around a SaaS model, and was all baked into Payload's frontend. Of course, it does use Payload on the backend (including the entirety of our old SaaS billing infra) but for those reasons, we did not open-source it.
However, v2 is coming and that will 100% be open-source!
However, v2 is coming and that will 100% be open-source!