I mean, if you're not trading(ie. you don't sell anything for real money with that name) how does it violate a trademark? I guess it may come down to that all items found on the server like Guild, Character, Item, etc. are property of GOA.
I think it is because GOA are trading, and it's technically them who are publishing your name (it's on their hardware and in the application they operate). That's why GOA are so interested in it. If it was the account holder liable, obviously GOA would be more likely to let you take your chances.
It's moot, though, whether you're trading. Unless a case can be made that you (through GOA) are offering a product or service in the same "NICE" category as the trademark holder, or that in some way your use of the trademark affects their ability to do so, there's no infringement. Someone earlier quoted this from Wikipedia, but you'll find exactly the same information if you look up the UK Inellectual Property Office (the offcial UK government office dealing with trademarks). Dunno about France or other countries, but trademark legislation is one of those areas that has been pretty thoroughly internationalised.