In short, the proxy lets you run NetMeeting sessions through a firewall.
NetMeeting and firewalls do not really mix. The problem is that NetMeeting uses a complex set of protocols (H323) that require it to be able to negotiate the use of arbitrary TCP and UDP ports in both directions. Such behaviour is difficult for a firewall to support in a secure way, because it has no knowledge of which ports are being used, and why. Things get even worse if the firewall has to do address translation.
Last upstream release is 2 1/2 years old.