Lua was initially designed as an embedded scripting language.The most popular applications built using Lua are games! It's also used a lot in building plug-ins, most often embedded into other languages. This tutorial explains nothing significant about meaningful programming using Lua : how to write functions? how to build Tables(most important data structures in Lua) Arrays? Object-oriented programming in Lua?
Lua was a boon to game enthusiasts with no programming experience. Can an amateur even start developing the simplest of games using this tutorial? I think not.
I am a big fan of Zed Shaw's tutorials, and if one wants to follow a similar trend, they should be more consistent with updating their material for everyone.