I'm hosting a server (listen), but my buddy can't join in-game, he's stuck up on the "connecting" screen... Is there a solution besides port-forwarding?

The very first step is the portforwarding. If it isn't done correctly, then the server can't leave your local network (can't pass the router). If you sure you did it correctly, then maybe your friend has a different version of the game. The GOG.com always sell the full patched versions. Of course if he has the GOG.com release too, this isn't problem.

The last thing I can say, check your IP address. Make sure you use the external and not the local address. The local address is only used by the router to differentiate the PCs within the internal network.