1) SpiceDB is fully open source. We do all development on it in the open and are collaborating with outside organizations and individual contributors. Authzed sells the serverless platform for SpiceDB or an on-premise version of that serverless platform. We want all of the tools that make developers successful at using SpiceDB to be open because it'll drive adoption of our products. SpiceDB is not the product.
2) We typically gauge interest from the community before implementing a new datastore. With proven demand, we will accept a contribution that implements one, so long as we think we can keep it maintained. I created an issue for gauging the interest of YugaByteDB here: https://github.com/authzed/spicedb/issues/427