open-kgo (Apache-2.0): one Python API across nine families of knowledge graph (RDF/SPARQL, property graphs, in-memory, agent-memory, and more): declare the traversal once, swap the backend by config. Plus an ontology layer that validates each traversal so semantically-invalid hops fail loudly instead of returning wrong answers. Runs offline, no Docker.
Early and two-person: feedback on the connector taxonomy (what family's missing) very welcome: https://github.com/mloda-ai/open-kgo
