Ok, doubt this will end the whole debate here but if you're curious about the Playshapes business, please check out this forum:
Playshapes, credited with making Bowser's Castle as far as I'm aware, made a second game called Legend of Krystal (Which you can find at that link.) He didn't finish it, but created the game so it was open source so anyone else could change or add to the game (this is where K Fox and the Magic Sword comes from).
Currently, a team of volunteers are working to update and continue work on this game by Playshapes. While he doesn't post in the general forum section anymore, he is supposedly active and staying in contact on the developer's forum. This doesn't mean it's a surefire way to contact Playshapes, but it certainly confirms his existence.
All in all, considering this and the fact that many months have passed without any progress or signs of upcoming updates from GaryuX28 at all, the evidence seems pretty damning that this work was stolen and will never actually be updated. All I see in the author's comments are a lot of ambitious ideas of which we've never seen any sample proof of. There's even the typical "Oh I was almost finished but then lost everything!" comment included above, which seems more like a way to keep putting everyone on.
Of course, I may be wrong about all this, but judging from the information I've seen, it certainly doesn't look good. I've come across this Bowser's Castle flash on other forums long before GaryuX28 posted it here. I've even seen a few altered, updated versions of it that he has not put here either.
In the end, without any brand new, unseen content updates from him, this debate will never end until people lose interest.