LuaExpat is still maintained! I released 1.3.0 in 2014 (which is in distros), and plan to release 1.4.0 soon™ with a number of changes, many from the original maintainer Tomas. It's overall a stable and finished library, so things don't move fast. However I and a bunch of active projects depend on it heavily. If you have any problems with it, now is a good time to report them so they can be included in the release (otherwise you may have to wait another decade!). The latest code is here:
https://code.matthewwild.co.uk/lua-expat