Serious answer: limiting to just Open Source: JanusGraph, DGraph, Apache AGE, HugeGraph, MemGraph and ArcadeDB all meet that criteria.

What is open source and what is a graph database are both hotly debated topics.

Author of ArcadeDB critiques many nominally open source licenses here:

https://www.linkedin.com/posts/garulli_why-arcadedb-will-nev...

What is a graph database is also relevant:

  - Does it need index free adjacency?
  - Does it need to implement compressed sparse rows?
  - Does it need to implement ACID?
  - Does translating Cypher to SQL count as a graph database?