MariaDB is a database server that offers drop-in replacement functionality for MySQL. It is built by some of the original authors of MySQL, with assistance from the broader community. In addition to the core functionality of MySQL, it offers a rich set of feature enhancements including alternate storage engines, server optimizations, and patches.
Infobright Community Edition (ICE) is an analytic database built on MySQL, designed to deliver very fast query response against large data volumes. It is a self-tuning, columnar database that eliminates the need to create or maintain indexes, partition data, or perform other administrative tasks.
libubiqx is an in-memory database suitable for use in embedded systems. The libubiqx database management system is a fully functional DBMS API that supports both hierarchical and relational data architectures. It provides developers with robust and scalable data management tools for use in embedded systems or SNMP agent applications.
hamsterdb Embedded Storage is an embedded database engine written in ANSI-C. It includes B+Trees with variable length keys and records. It supports in-memory databases and endian-independent files, database cursors, multiple databases in one file, "record number" databases, and duplicate keys. hamsterdb is very fast and highly configurable. It compiles and runs on Unix platforms, Linux, Microsoft Windows, and Windows CE.