It's a bit unclear what exactly are you asking for. Have you got a MUD server already? If what you mean scripts for it, then you'r probably be writing the script, uploading it to the server (or writing it on the server directly) and then reloading it in the Lua VM. There isn't a problem of blocking user input here, so perhaps I'm misunderstanding you.

For a Lua MUD server, check out MudCore, which is build on pretty good stuff. I can't vouch for how well it would perform, I've only fiddled with it a bit, but the tech behind it is pretty solid.

It's cross-platform as well so you wouldn't be getting tied down to finding a Windows server for your hosting.

It's a bit unclear what exactly are you asking for. Have you got a MUD server already? If what you mean scripts for it, then you'r probably be writing the script, uploading it to the server (or writing it on the server directly) and then reloading it in the Lua VM. There isn't a problem of blocking user input here, so perhaps I'm misunderstanding you.

For a Lua MUD server, check out MudCore, which is build on pretty good stuff. I can't vouch for how well it would perform, I've only fiddled with it a bit, but the tech behind it is pretty solid.