However, LuaTeX team changed them significantly after ver. 0.80. Yes. And more changes will surely come, at any and every level -- no stability has ever been guaranteed until 1.0, for which there is no ETA.
E.g., the latest news is that (as I understand it) LuaTeX ignores \language0 and thus does not hyphenate normal English by default. I don't know how to restore the standard behavior. http://tug.org/pipermail/luatex/2016-February/005685.html Hans told me there is a file luatex-pdf.tex in the ConTeXt distribution that shows the changes. I can also send you guys preprints of a couple of short articles by him for the next TUGboat describing (some of) the changes, if you want. If it were up to me, I would simply declare LuaTeX unsupported at least until 1.0. It seems that tracking Hans's changes from now on will imply a huge investment of time and effort, let alone doing it in a compatible way so that people not running the bleeding edge will keep working as well. I don't see that the return is worth it. But of course, if you want to, more power to you! Best, Karl
