Java library implementing several transfer, authentication and encryption protocols
Specifically, OPAL implements the Global Platform 2.x card specification, a "a secure, dynamic card and application management specification that defines card components, command sets, transaction sequences and interfaces" (Wikipedia).
The GUI tool will allow you to manage various implementations of the specification.
OPAL is a cross-platform utility capable of running on any operating system that comes with Java support (e.g. Mac OS X, Windows, Linux).