[ What is this? ]
This development branch of eAthena uses Lua 5.0.2 as scripting language.

[ How to compile? ]
To compile it properly, you need to install Lua libraries (exactly like you need MySQL libraries to compile the SQL version).
First, download them from http://www.lua.org/ftp/lua-5.0.2.tar.gz, then extract them (under Linux, use tar and gzip tools; under Windows, use WinRar for example).
Navigate to the extracted folder (with Cygwin if you are under Windows).
Type in "./configure" and let it do all its stuff.
Type in "make" and let it do all its stuff.
Type in "make install" and let it do all its stuff.
You can now compile the Lua branch as any other, using the "make" command.

[ About ]
You can visit Lua website at http://lua.org
The licence notice for Lua is at http://www.lua.org/license.html