I just saw this in the Japandemonium Column in rpgamer.com

Quoting the words of the column's author:

"This is an item for all those parents out there who hear their kids talking about stuff like Naruto and have no idea what language is being used. It certainly isn't English at times, and some Japanese would make the argument that it's not their language either. The Japan Foundation is out to bridge the generation and culture gap with a new website dedicated to the language, jargon, and expressions specific to manga and anime.
The site's just gone up this past Monday, so it's still a work in progress. Among the upcoming features there are genre-specific games and quizzes pertaining to useful words and kanji. So if you find yourself wondering what the heck kids these days are talking about, here's some help."

http://anime-manga.jp/

That description doesn't match the site at all. It's 100% not what it's about. At least, not so far.

As for the Japanese saying it's not their language, welcome to the club! They've been murdering English for a long time now. I cringe every time I hear some broken english that they've made into slang.