The DMCA isn't a problem; feel is hard to copyright. And if Google now owns the IP, they don't give two shits about suing somebody making a copycat app of something they abandoned.
The problem is that good UI takes an absurd amount of work. It's the difference between painting a wall and painting a mural. With Sparrow to copy you'd have a good start, but you have to be enough of a UI devotee to even notice what makes a UI strong, and you'll still have to do a lot of user testing and polish.
The problem is that good UI takes an absurd amount of work. It's the difference between painting a wall and painting a mural. With Sparrow to copy you'd have a good start, but you have to be enough of a UI devotee to even notice what makes a UI strong, and you'll still have to do a lot of user testing and polish.