It's been out for sometime now. Probably since 2014-15. I got mine off AliExpress for like $10 and got gifted the box, manual and label. I gave it a play through in 2016 and thought it was ok. Definitely a fan hack as it's not the exact same as Pokemon yellow. For some reason I think some of the typing was wrong? Like fairy moves weren't fairy? They were normal. Idk I could be wrong I haven't played it since.
Yep just checked, AliExpress still has em for $15 shipped. Anyone paying eBay price for Chinese knock offs is insane.
I'm pretty sure the box, manual are designed by the host of the website http://thisroomisanillusion.com John Miller. He was a member of NA but I can't remember his user name. His website has his most recent work of ninja gadian.