[elliottcarlson]

I assume a non-clean-room design -- looking at the code and reinterpreting it to be different enough.

https://en.wikipedia.org/wiki/Clean_room_design

[loup-vaillant]

If it was just that, it would be legal.

Clean room is a way to prove you couldn't possibly have infringed copyright. It is not mandatory.

[elliottcarlson]

Right - the point is that it would be non-clean room.