LemonGraph is described as 'An embedded transactional graph engine for Python' and is an app in the Development category. There are more than 10 alternatives to LemonGraph for a variety of platforms, including Linux, Mac, Windows, Self-Hosted solutions and Python. The best alternative is SQLite, which is both free and Open Source. Other great apps like LemonGraph are Firebird (Free, Open Source), Wikibase (Free, Open Source), ArangoDB (Free, Open Source) and neo4j (Free, Open Source).
SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine. SQLite is the most widely deployed SQL database engine in the world. The source code for SQLite is in the public domain.
Firebird is a relational database offering many ANSI SQL-92 features that runs on Linux, Windows, and a variety of Unix platforms. Firebird offers excellent concurrency, high performance, and powerful language support for stored procedures and triggers.
Wikibase is the software that runs Wikidata, but is also usable for other projects beyond that. Wikibase allows the collaborative editing of structured data on top of MediaWiki. It is optimized for graph-like, schema-poor data, not for tabular and strongly pre-structured data.
RedisGraph is a property graph database module for Redis. It is the first graph database to use linear algebra on sparse adjacency matrices to implement graph operations, which lets it achieve high performance. It understands OpenCypher queries.