From http://www.zeromq.org/  and http://github.com/tybor/Liberty/tree/master/src/wrappers/zmq

ezmq is based on zmq Liberty wrappers.

ØMQ is a lightweight messaging implementation with socket-like API.
ØMQ supports different messaging models (publish/subscribe, request/reply, streaming).
ØMQ is already very fast. We're getting 13.4 microseconds end-to-end latencies and up to 4,100,000 messages a second today.
ØMQ is very thin. Requires just a couple of pages in resident memory.
ØMQ is fully open sourced LGPL-licensed software written in C++.
ØMQ provides C, C++, Common Lisp, Java, Python and Ruby language APIs.
ØMQ supports different transport protocols: TCP, UDP, PGM, IPC, inter-thread etc.
ØMQ runs on AIX, FreeBSD, HP-UX, Linux, Mac OS X, OpenBSD, OpenVMS, QNX Neutrino, Solaris and Windows.
ØMQ supports i386, x86-64, Sparc, Itanium, Alpha and ARM microarchitectures.
ØMQ is fully distributed: no central servers to crash, millions of WAN and LAN nodes.