Your analogies just sounds like general consequences of market competition.

and there is no good-guy when it comes to the story of facebook.

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I guess my only takeaway is that if I want to protect my IP then anyone who has access to the software should be required to sign a terms & agreement that specifically written to prevent this kind of thing, regardless IANAL, but i’m pretty sure this is all legal according to copyright law. The engine and therefore the code is different, the assets are custom and slightly different. If this were a trademark or patent related case then there might be a something else to go on.