For various reasons, now seemed like a good time to release the mnet server executable. I don't think there is any danger of breaking up the community by making it available, and I thought some people might enjoy seeing what it's like, so...
Grab the install file from the link below (Windows only). It will install everything you need for a fully functional mnet server, except user accounts. Read the readme.txt and documentation.txt files after installation, and follow the steps to get it up and running - you basically just have to create a couple user accounts, configure some options from the server, point your myth client to it, and off you go.