A lot of PC RPGs follow in the tradition of Ultima / Early Fallout / Baldur's Gate / Icewind Dale / etc. They are primarily isolinear and heavily mouse driven. A lot of free/open source GNU/Linux RPGs follow suite, which means they would need quite a user interface and input overhaul before they would work comfortably on the GCW Zero. I myself ported over the 'Exult' engine
to play Ultima 7 but without a keyboard and with current mouse emulation it isn't the most polished experience.
There is a developement build of EasryRPG
which allows playing select RPG Maker games (though it has limited/low compatibility now. In theory that could improve with time.)Monster RPG 2 is free/open source
and uses Allegro as the back end. Allegro is likely able to be built on the GCW from my understanding, though I wager the game engine would have to be modified for our screen resolution.
That being said if you are looking for JRPGs and you want something new, there are a wealth of JRPGs
outside of the more well known titles. Many of which can be emulated on the GCW Zero, Translation groups still release new patches for games we never got in the west, so its very likely there are quite a few gems out there which are 'effectively new.'