LuaTeX

LuaTeX is a TeX-based typesetting engine that embeds the Lua scripting language to extend TeX with programmable control over typesetting. It provides two-way communication between TeX and Lua, allowing users to execute Lua code from within TeX and to expose TeX internals to Lua.

Development and distribution: The project is open-source and maintained by the LuaTeX community, with releases bundled in major TeX distributions such as TeX Live and MiKTeX. It originated as an alternative TeX engine designed to combine TeX's high-quality typesetting with Lua's programmability and supports modern font technologies.

Key features: Embedded Lua interpreter; direct Lua integration via the \directlua primitive; a robust font subsystem based on a Lua-based font loader to support OpenType fonts; extensive programmable access to TeX's nodelists and page-building; ability to write packages or modules in Lua; improved macro authorship and automation capabilities.

Usage and ecosystem: In practice, LuaTeX is commonly used with LaTeX as LuaLaTeX, a variant that combines the LaTeX macro package with the LuaTeX engine. The combination enables enhanced customization, complex typesetting tasks, advanced font handling, and scripting possibilities that extend standard TeX workflows. LuaTeX remains a core component of modern TeX distributions and a popular choice for users needing programmable extensibility.