Comment by Rochus

Thanks for the hints. The projects have different goals. My goal is to use a stand-alone luatex engine and integrate it with my new typesetting language, completely replacing TeX. MMTeX still uses TeX, but make an easier to install package using the OpTeX format; that's a very good approach for people who want to use OpTeX and don't care about the whole TexLive machinery. Speedata is closest to what I intend, but their language is XML based and optimized for catalogues, and they depend on a pre-existing luatex installation (so they could use mine instead). LuaMetaTeX is the successor of LuaTeX which essentially moves more implementation to Lua. To my surprise, I actually didn't find a pre-existing project so far which shares my goals.