Apparenly Ryan Dahl considered Lua, but he rejected it because "Lua is less ideal but a lovely language - I did not like that it already had a lot of libraries written with blocking code. No matter what I did, someone was going to load an existing blocking Lua library in and ruin it."[1]

[1] http://bostinno.com/2011/01/31/node-js-interview-4-questions...