Due to the way system messages and other server features work in PWO, it would not be possible to implement multilingual support without a significant overhaul of the entire system. NPCs COULD potentially offer multiple languages, but this would make their scripts unfeasibly large and would slow down the game or make NPCs very laggy. We DO, however, permit people making skins in other languages so that the interface and general look of PWO can be translated to whatever language you may prefer, even if the game itself will remain in English.
Multi-lingual support for our web content is something we remain very interested in working on; one part of the recent Playerdex revamp was to implement support for alternative languages in the future.