Henry Minsky has done Japanese sites, and at one point there was a small but active group of Japanese using ACS 3.x (Henry lived in Japan for a year or two IIRC)
This led to the charset patches in AOLserver3.3+ad13. These have been adapted to AOLserver 4 (still in beta) but I don't know if anyone's done significant testing in Japanese or Chinese yet.
PostgreSQL works fine with Japanese - there are Japanese developers involved in the project. Oracle, of course, should have no problem with any language charset either.
I know Greenpeace did testing with a variety of languages but I don't think they've actually rolled a live site with Japanese yet.
