Cool article... didn't know about ComputerCraft. Looks neat. :)
You can get multi-threaded/multi-process concurrency by messaging between separate Lua VMs, using libraries such as Lua Lanes (http://kotisivu.dnainternet.net/askok/bin/lanes/). The Lua VM is implemented without static state, so several VMs can run in the same process without a GIL.
There is LuaPi (https://github.com/LuaDist/luapi), an implementation of the Pi calculus (a variant of CSP), but I don't really know much about it. I'm more familiar with Erlang-flavored concurrency models (and there's also ConcurrentLua, https://github.com/lefcha/concurrentlua).
luaproc as described in http://www.inf.puc-rio.br/~roberto/docs/ry08-05.pdf is nice and simple. I'm also interested in lua-zmq.threads for LuaJIT which uses zeromq for message passing between threads. http://lua-users.org/lists/lua-l/2011-04/msg00364.html and https://github.com/Neopallium/lua-zmq