In theory this is not needed. This port does not need bison.
One of its dependent ports (openh323) needs bison and openh323
already has USE_BISON in its makefile.
However, without this bento complains that the port needs
bison and fails to build the package.
This is a H323 Gatekeeper for H323 compliant videophone programs
such as voxilla, OhPhone and OpenPhone (see /usr/ports/net/openh323)
and commericial programs like NetMeeting.
More information can be found at
http://www.opengatekeeper.org