On BSD (including Mac OS X) SO_REUSEPORT should be specified along with SO_REUSEADDR to match behavior on Linux (and possible Windows). This is needed to have multiple listeners to a UDP broadcast.
I discovered this when using PyOSC. Attached is an example modified to subclass SocketServer with a workaround. It should be possible to start multiple instances of this program, all of which will receive messages to a broadcast address (eg 255.255.255.255:7110).
This test uses Python 2.7 on OS X (despite the "python3" shebang line from the example)