Tita's House of Games is run by Carl Brodt and his wife Tita, and they're good friends of Tadashi Ehara (of DWP). They're nice folks, and have lots and lots of Tekumel materials available for sale---original editions, as well as various reprints that Carl has done over the years.
The Tri-Stat version of Tekumel was published by the-now-defunct Guardians of Order, and I don't think that Mark got around to publishing the
d20 version before GOO folded. GOO has no relation to Tita's House of Games.