Our policy here is that it's fine to post here anything that's in any of the major PD book collections. From a practical perspective, nobody's going to get into trouble posting as a free download something that anyone can download themselves, so go ahead and do the Robert Howard stuff if you wish. We would, of course, respect a formal request by the US copyright holder to remove it, but the chances of that happening are, to put it mildly, not large. It would be a different matter if you tried to sell it commercially in the US, but I think we can assume that you're not going to do that, can't we?