Apache ActiveMQ ™ -- OpenWire C Client
Connectivity > Cross Language Clients > C Integration > OpenWire C Client
This is the C library which is based on the OpenWire protocol.
You can browse the code here
http://svn.apache.org/repos/asf/activemq/sandbox/openwire-c/
e.g. here's an example of it in use...
http://svn.apache.org/repos/asf/activemq/sandbox/openwire-c/src/examples/main.c