Berkeley DB (libdb) is a programmatic toolkit that provides embedded database support for both traditional and client/server applications. It includes b+tree, queue, extended linear hashing, fixed, and variable-length record access methods, transactions, locking, logging, shared memory caching, database recovery, and replication for highly available systems. DB supports C, C++, C#, Java, PHP, and Perl APIs. It supports key-value pair (NoSQL), SQL, and Java Object formatted data. It is available for a wide variety of Unix platforms as well as QNX, Android, Mac OS X, and several varieties of Windows.
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.
db4o is an object database for Java and all .NET environments. Its features include ACID transactions, automatic class schema recognition, query-by-example, a S.O.D.A. object querying API, native queries, LINQ support on .NET, callback methods, memory files, cascade-on-delete, multi-threaded access, and Java Webstart and servlet support.
CodeBase is a high-speed xBASE compatible database engine for C/C++, Visual Basic, Delphi & Java programmers. You can use CodeBase to write high performance database applications that are multi-user compatible with FoxPro, dBASE and Clipper, create anything from a Java applet to a full-blown Windows database application to a simple DOS utility, write scalable applications that can be deployed as single-user, multi-user or client/server, all without changing any of your source code, and port your applications to Windows, DOS, UNIX, OS/2, and Macintosh. There's a free 30-Day Test Drive option available. CodeBase is available for every major operating system including Windows XP, 2000, 9x, NT, CE, DOS, OS/2, Macintosh, and a variety of Linux and UNIX platforms including Solaris, SunOS, HP/UX, AIX, SCO, and others.
VoltDB is a blazingly fast relational database system. It is specifically designed to run on modern scale-out architectures: fast, inexpensive servers connected via high-speed data networks. It is aimed at a new generation of database applications - real-time feeds, sensor-driven data streams, micro-transactions, low-latency trading systems - requiring database throughput that can reach millions of operations per second. What’s more, the applications that use this data must scale on demand, provide flawless fault tolerance, and enable real-time visibility into the data that drives business value. It includes client application drivers for applications written in Java, C++, C#, PHP, and Python. VoltDB community members have also authored client libraries for Erlang, Ruby and Node.js. There are streaming export capabilities for leading analytic database environments, including Apache Hadoop.
DeveelDB is an embedded SQL database management system for .NET, implementing all the features of the SQL92 specifications (transactions, triggers, procedures, functions, etc.). The aim is to provide .NET and Mono developers with a fully functional, powerful, and embeddable database system that can be used in several contexts, managing small to large amounts of data.