Brandon Sheffield:
Within the casual space, I've been having to revise my idea of what a "clone" is, because there's a lot of them. You could describe a lot of PopCap games that way, as well. Like AstroPop and Zuma. Since the casual space has a narrower focus, it seems really tough to know whether you're using a similar mechanic and tweaking it -- which happens all the time in larger games -- or functionally cloning.
Jason Kapalka:
We've been accused of ripping off of some games. At the same time, you don't usually hear people saying that World of Warcraft ripped off EverQuest. Or that Half-Life ripped off Quake. The similarities are pretty close; you can't imagine how World of Warcraft could have existed without EverQuest. It's not possible. Or any of games now, without World of Warcraft.

I don't know; it's kind of a tricky thing. Personally, I like if games borrow stuff from our games, then add something new to it. I'm usually pretty happy about that. Puzzle Quest or Jewel Quest, or some other games where they've taken the Bejeweled mechanic and done something interesting with it, I generally feel pretty cool about that.

And I hope that when we do things that are building on earlier game mechanics, that we also at least add something new to it. What sucks is if you make a clone or a derivative game that is worse than the original, and doesn't really add anything.

If you're iterating on it, and adding something that wasn't there before, if it enhances the field of game design, I think that's worth doing. That may be different from what a legal definition would be, but, [it's] the moral/ethical [definition]. If you actually make the game better, you could argue that you have a right to do it.