I used it to build a ton of opensource stuff in addition to the company I founded. I use it every day and I'm very happy with how it's turned out. I regret not updating the language more frequently, but I've been busy building a bunch of stuff in it.
The biggest open source project is a web framework for Open Resty: https://github.com/leafo/lapis
It's used for the following open source websites: https://github.com/luarocks/luarocks-site https://github.com/leafo/streak.club
The company I made, https://itch.io also runs on it. There are a a ton of extra Lua modules I've made in MoonScript to facilitate it. Here's a list of my published modules: https://luarocks.org/modules/leafo
I've also completed Ludum Dare 11 times now, making a game each time in MoonScript. I've used https://love2d.org/ as the game engine. You can find the games on my GitHub: https://github.com/leafo?tab=repositories
Feel free to ask any questions