When people say 'official conan RPG' what is that in reference to exactly (I was under the impression that the Howard stories were all in the public domain---is that not the case?)
The issues with Conan are not that cut and dried.
The last of REH's released-in-his-lifetime works are not in the public domain
in the US. The copyrights were extended, so, being post Steamboat willy, it's life + 95 years. He died in 1936, so.. 1941... 2031. 7 more years for the last of them. (Note that Australia has a shorter copuyright term, so many things are on Gutenberg.net.au that are not yet on gutenberg.org. Including certain Howard and Borroughs works.)
But Howard actually isn't the most prolific of the Conan authors. Lin Carter, L. Sprague deCamp, Donald M. Grant, and others have written as much or more each, and those works are all still in copyright.
The estate, I don't know if it's a corporate entity, or just IP ownership, also owns the Trademarks.
Astonishing Swordsmen and Sorcerers, for all it's derivation from Howard's work, and legit being able to do so under copyright, can't use "Conan" in the name, because it's a trademark owned by the estate's ownership.
In Howard's time, it was a proposed name for a lost continent in the then recently (1912) introduced theory of Continental Drift. That Howard may have been the inspiration for that cannot be ruled out, and Howard is partly why it was rejected.
There was a TSR era one that wasn't AD&D (at least as I recall).
That's the color table one I mentioned. Its adventures had a different code than the AD&D ones. Conan: The Roleplaying Game. It plays just fine. It's also the basis for the ZeFRS (Zeb's Fantasy Roleplay System) pseudoclone.