MariaDB 5.5 is the previous stable (GA) release of MariaDB. It is MariaDB 5.3 + MySQL 5.5.
See "What is MariaDB 5.5" for an overview of what is in MariaDB 5.5.
The MariaDB Client for Java is used to connect applications developed in Java to MariaDB and MySQL databases. The client library is LGPL licensed.
See this article for more information
MariaDB Connector/C is used to connect applications developed in C/C++ to MariaDB and MySQL databases.The library is LGPL licensed.
See the MariaDB Connector/C section of the MariaDB Knowledge Base for more information.
MariaDB Connector/ODBC is an LGPL licensed, standardized database driver for Windows platforms. It supports ODBC Standard 3.5 and can be used as a drop-in replacement for MySQL Connector/ODBC.
The MariaDB Connector/ODBC section of the MariaDB Knowledge Base contains more information.