LuaTeX is an extended version of pdfTeX using Lua as an embedded scripting language. The LuaTeX project's main objective is to provide an open and configurable variant of TeX while at the same time offering downward compatibility. From the user perspective we have pdfTeX as stable and more or less frozen 8 bit engine, XeTeX as unicode input and font aware engine using libraries for font handling, and LuaTeX as engine that is programmable and delegates as much as possible to Lua, with the objective to keep the core engine lean and mean. Each engine has its benefits and drawbacks (more details here).
At the TUG 2007 conference in San Diego, the first public beta of LuaTeX was presented. Most of that day was dedicated to the project, its outcomes and its objectives (this project is partly driven by the oriental TeX project). Although intermediate version could be used for production the first stable release happened at the 10th ConTeXt meeting in 2016 in the Netherlands.
There are three closely related projects (see download for svn details):
The first two projects result in a collection of OpenType fonts that can be used in LuaTeX and XeTeX. The third project results in a MetaPost library (to be used in LuaTeX) and a version of MetaPost (written in C) that can handle larger quantities and fulfills some long standing wishes of the MetaPost development team.
All these projects report on a regular basis in (local) TeX usergroup journals and at TeX related conferences. Normally the most recent information can be acquired in the ConTeXt universe: mailing lists, source code, status documents and manuals.
On TeXlive 2016 you can find the stable release 0.90. In September 2016 we released version 1.0 which will be on TeXlive 2017. You can fetch the latest binaries for quite some platforms from The ConTeXt Garden or compile them from source yourself.