Top 2 multi-model-dbms open source projects

OrientDB is the most versatile DBMS supporting Graph, Document, Reactive, Full-Text and Geospatial models in one Multi-Model product. OrientDB can run distributed (Multi-Master), supports SQL, ACID Transactions, Full-Text indexing and Reactive Queries. OrientDB Community Edition is Open Source using a liberal Apache 2 license.

Graph database optimized for fast analysis and real-time data processing. It is provided as an extension to PostgreSQL.