MUSCLE (Multi User Server Client Linking Environment) is an N-way messaging server and networking API. It includes client-side networking APIs for various languages, including C, C++, C#, Delphi, Java, and Python. MUSCLE lets programs communicate over a network via streams of serialized Message objects. The included server program ("muscled") lets its clients message each other and store information in its server-side hierarchical database. The database supports flexible queries via hierarchical wildcarding, and "live" updates via a subscription mechanism.
HSQLDB (HyperSQL DataBase) is an SQL relational database engine written in Java. It supports nearly full ANSI-92 SQL and SQL:2008 enhancements. It is a small, fast multithreaded, and transactional database engine which offers in-memory and disk-based tables and supports embedded and server modes.
KInterbasDB is a Python extension package that implements Python Database API 2.0-compliant support for the open source relational database Firebird and some versions of its proprietary cousin Borland Interbase. In addition to the minimal feature set of the standard Python DB API, KInterbasDB also exposes nearly the entire native client API of the database engine.
DB_DataContainer is a PEAR-compliant database persistence layer and data encapsulation class. It encapsulates the behavior required to make objects persistent, including loading, saving, and deleting objects in a persistent store. It currently supports relational databases and uses PEAR DB for database abstraction.
dbo is yet another database object framework written entirely in Python. Tables are represented using schema objects that encapsulate column information and supporting metadata. Row instances are represented as a dictionary. Features include database independence (with Postgres and MySQL support), automatic type conversion, database schema extraction, sequence emulation, on-the-fly table joins, and more.
SibylSQL is a portable, full-fledged, next-generation, client-server, multi-threaded, object-relational database system. The primary technical contribution to the database community is the inclusion of the SQL Dialect Interface (SDI), originally written for the NightStar NEXTGRES database. The SDI allows a DBA to grant users or applications the ability to translate vendor-specific SQL such as Oracle, SAP DB, MSSQL, and PostgreSQL, into a native SibylSQL parse tree via dynamically loadable objects at run-time.