Hi, in order to have other folks outside your network speak to Murmur, you'll have to port forward whatever port it's running on, over both TCP and UDP.
My experience has been with folks running servers from home that it's generally a recipe to hate life. Some consumer routers aren't good enough to throw multiple streams of tiny UDP packets around, your ISP may hate it too, and Mumble doesn't deal with NAT super gracefully in my limited experience.
I'd wholeheartedly recommend either renting a server, renting a small VPS to run it from, or using one of the many public ones. Feel free to try port forward 64738 TCP/UDP to Murmur's internal IP, and then hand out your external IP to other users though.