Vysper depends on these fine libraries and frameworks:

MINA - for socket communication.

Spring Framework (optional) - for component configuration and wiring.

Bouncy Castle SSL Provider - stream encryption

JUnit - unit testing

slf4j - logging framework, currently using log4j, but this is exchangable

Jackrabbit - Jackrabbit is used for JCR container persistence.

More detailed info about dependencies and libraries can be found here.