Starting with version 10 upslug2 is compatible with Mac OSX.
Upslug2 requires libpcap version 0.9.3 or greater to work on OSX. By default,
libpcap is included in OSX but it doesn't support all needed functions. So you
will need to install a more recent version of libpcap. Fortunately the library
is available through DarwinPorts (http://www.darwinports.org). Maybe it is also
available from Fink (http://fink.sourceforge.net) but that has not been tested.
If you don't have DarwinPorts installed, go to the website and learn how to
use it. Just make sure you also install libpcap.
Now you are ready to build upslug2:
By default, DarwinPorts will be installed in /opt. If you have it installed
in another location you have to adjust the path's below.
CPPFLAGS=-I/opt/local/include LDFLAGS=-L/opt/local/lib ./configure --with-libpcap
Using upslug2 requires root access since the bpf-device(s) on OSX are
configured for read-only access for all other users.