I think this is only "not nice" because of the dcurtis's reaction. He could have very easily just replied "Cute." to this thread and accepted the flattery/parody. No one is arguing that "obtvse" is a better product than his own.
For instance, the author of http://drawar.com/ is clearly flattered by dcurtis's own use of his design.
I guess that's what I meant by "good faith". I think making a nigh identical open copy of someone's work is easily predictable to be unpleasant for many people. In plenty of situations (esp on HN and its environs) this is not the case, you can have a reasonable expectation that the person whose work you've been "inspired" by would approve, maybe grudgingly.
I think that in this particular situation, dcurtis's reaction could have been predicated to be at best ambivalent. Thus, choosing to take the liberty of going ahead I consider as "not nice".
Those are about the strongest terms with which I can condemn it though. In another reply to my comment zackattack mentions dcurtis himself isn't nice. That may be the case (although I've seen his name plenty, I'm having enough trouble connecting it to specific writings that I can't agree or disagree), but the crucial issue to determining whether this project is "nice" or not, is whether it was reasonable to expect this action to hurt dcurtis. It clearly did, and since I think that was a plausible outcome, I am uncomfortable with this undertaking.
For instance, the author of http://drawar.com/ is clearly flattered by dcurtis's own use of his design.