Thanks, I've seen that. So far kpathsea didn't get into my way and caused less trouble than the Lua code I had to use to (hopefully) achieve optimal typsetting

Thanks, I've seen that. So far kpathsea didn't get into my way and caused less trouble than the Lua code I had to use to (hopefully) achieve optimal typsetting quality. But kpathsea is indeed on my list of disposable parts. And for a system like speedata at least the Lua implemented luaotfload machinery had to be accessible somewhere in a known directory. When they now switched to LuaHBTex (as I likely will as well) this dependency can be avoided without losing typesetting quality (as far as I've understood so far).